777-2.pdf

Service Training Meeting Guide 721

SESV1721 January 2000

TECHNICAL PRESENTATION

777D UPDATE (AGC) OFF-HIGHWAY TRUCK

777D UPDATE (AGC) OFF-HIGHWAY TRUCK MEETING GUIDE 721

SLIDES AND SCRIPT AUDIENCE

Level II--Service personnel who understand the principles of machine systems operation, diagnostic equipment, and procedures for testing and adjusting.

CONTENT This presentation provides basic maintenance information and describes the systems operation of the engine, power train, steering, hoist and the air system and brakes for the 777D Update Off-highway Truck. The Automatic Retarder Control (ARC) and the Traction Control System (TCS) are also discussed.

OBJECTIVES After learning the information in this meeting guide, the serviceman will be able to: 1. locate and identify the major components in the engine, power train, steering, hoist and the air system and brakes; 2. explain the operation of the major components in the systems; and 3. trace the flow of oil or air through the systems.

REFERENCES 777D Update (AGC) Off-highway Truck Service Manual 777D Update (AGC) Operation and Maintenance Manual 777D Update (AGC) Parts Manual

RENR3330 SEBU7261 SEBP3016

PREREQUISITES Interactive Video Course "Fundamentals of Mobile Hydraulics" Interactive Video Course "Fundamentals of Electrical Systems" STMG 546 "Graphic Fluid Power Symbols"

Estimated Time: 24 Hours Visuals: 206 (2 X 2) Slides Form: SESV1721 Date: 01/00

TEMV9001 TEMV9002 SESV1546

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SUPPLEMENTAL MATERIAL Reference Manuals Fluid Power Graphic Symbols User's Guide Cold Weather Recommendations for Caterpillar Machines Caterpillar Machine Fluids Recommendations

SENR3981 SEBU5898 SEBU6250

Specification Sheets 777D Off-highway Truck

AEHQ5140

Salesgrams and Product Bulletins Salesgram "Cat 777D Update Off-highway Trucks" Product Bulletin "Caterpillar 777D Off-highway Trucks" (3PR serial number) Training Bulletin "Caterpillar Transmission/Drive Train Oil" Product Bulletin "Reporting Particle Count By ISO Code" Salesgram "Caterpillar Extended Life Coolant" Product Data Sheet "Caterpillar Extended Life Coolant"

TELQ3747 TEJB3015 TEJB1002 PEJT5025 TEKQ0072 PEHP4036

Technical Instruction Modules Caterpillar Monitoring System--769D - 777D Off-highway Trucks 769C - 793B Off-highway Trucks--Torque Converter and Transmission Hydraulic Systems 769C - 793B Off-highway Trucks--Air System and Brakes Automatic Retarder Control System Automatic Electronic Traction Aid 769C - 793B Off-highway Trucks--Suspension System Truck Payload Measurement System

SEGV2622 SEGV2591 SEGV2595 SEGV2593 SEGV2585 SEGV2599 SEGV2579

Service Training Meeting Guides STMG 681 "3500B Engine Controls--Electronic Unit Injection (EUI)"

SESV1681

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SUPPLEMENTAL MATERIAL (Continued) Video Tapes Suspension Cylinder Charging TPMS Management/Technical Information TPMS Operating Tips Introduction to the Automatic Electronic Traction Aid Mining Trucks--Cleanliness and Component Life Oil Sampling--The Right Way

TEVN2155 AEVN2211 AEVN2212 SEVN9187 SEVN4142 PEVN4638

Booklets C-Series Mining Trucks--3500B Diesel Engines Know Your Cooling System Diesel Fuels and Your Engine Oil and Your Engine Understanding The S¥O¥S Report

LEDH8400 SEBD0518 SEBD0717 SEBD0640 TEJB1015

Special Instructions Accessing Flash Software for Machines Caterpillar Electronic Controls Service Code Information Description List Adjustment Of The Valve Lash And The Valve Bridge With The 147-5482 Valve Lash Gauge Group Using the 8T8697 Electronic Control Analyzer Programmer (ECAP) Using the ECAP NEXG4521 Machine Functions Service Program Module Using the 7X1700 Communication Adapter Group Use of CE Connector Tools Servicing DT Connectors Parts Listing Of The Deutsch Connectors And Components Use of 6V3000 Sure-Seal Repair Kit Use of 8T5200 Signal Generator/Counter Group Suspension Cylinder Servicing 777D Assembly Procedure

REHS0494 REHS0126 REHS0128 SEHS8742 SEHS9343 SEHS9264 SEHS9065 SEHS9615 REHS0148 SMHS7531 SEHS8579 SEHS9411 REHS0563

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SUPPLEMENTAL MATERIAL (Continued) Brochures Caterpillar Electronic Technician Caterpillar DataView Diesel Engine Oil (CH4) Product Data Sheet How to Take a Good Oil Sample S¥O¥S Coolant Analysis Air Filter Service Indicator Caterpillar Fully Automatic Transmission Cat Oil Cooled, Multiple Disc Brakes Caterpillar Automatic Retarder Control Caterpillar "D" Series Truck Cabs Caterpillar Truck Frames Mining Truck Bodies: Selecting The Right Body System For Your Job Caterpillar Truck Production Management System: Answering your questions about TPMS

NEHP5614 NEHP5622 PEHP8038 PEHP6001 PEHP5033 PEHP9013 AEDQ0066 AECQ5980 AEDK0075 AEDK0706 AEDK0707 AEDK0083 AEDK2953

Miscellaneous Pocket Card "Electronic Diagnostic Codes" Chart "Practical Pressure Conversions" "Cleaning Rear Axle Housing Assemblies (785/789)" Training CD-ROM "Caterpillar Electronic Technician (ET) for Off-highway Trucks" Training CD-ROM "Truck Production Management System (TPMS) for Off-highway Trucks"

NEEG2500 SEES5677 SEBF8366 SERV7003 SERV7004

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TABLE OF CONTENTS INTRODUCTION ........................................................................................................................7 MAINTENANCE .......................................................................................................................11 OPERATOR'S STATION............................................................................................................42 Machine Controls..................................................................................................................44 Caterpillar Monitoring System .............................................................................................50 Truck Payload Measurement System (TPMS)......................................................................74 ENGINE......................................................................................................................................77 Engine Electronic Control System .......................................................................................78 Cooling Systems ...................................................................................................................93 Jacket Water Cooling System .........................................................................................94 Aftercooler Cooling System ...........................................................................................99 Lubrication System .............................................................................................................103 Fuel System.........................................................................................................................107 Air Induction and Exhaust System......................................................................................112 POWER TRAIN .......................................................................................................................119 Torque Converter ................................................................................................................120 Torque Converter Hydraulic System ..................................................................................123 Transmission and Transfer Gears........................................................................................135 Transmission Hydraulic System .........................................................................................136 Rear Axle ............................................................................................................................152 Transmission/Chassis Electronic Control System ..............................................................154 STEERING SYSTEM ..............................................................................................................171 HOIST SYSTEM ......................................................................................................................187 AIR SYSTEM AND BRAKES ................................................................................................209 Air Charging System...........................................................................................................213 Brake Systems.....................................................................................................................220 BRAKE ELECTRONIC CONTROL SYSTEM ......................................................................257 Automatic Retarder Control (ARC)....................................................................................261 Traction Control System (TCS) ..........................................................................................266 CONCLUSION.........................................................................................................................275 SLIDE LIST..............................................................................................................................276

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1 INTRODUCTION • Fuel tank

Shown is the right side of a 777D Update truck. The fuel tank is located on the right side of the truck.

• Front brake options

The standard 777D Update truck has front caliper disc brakes. Oil cooled front brakes are available as an option. Both brake types are covered in this presentation.

• Features and improvements

The major features added to the 777D Update truck are: improved cab, two Electronic Control Modules (Transmission/Chassis and Brake), a pressure compensated steering system and an electronically controlled hoist system.

• General specifications

Some of the specifications of the 777D Update Truck are: - Serial No. Prefix: AGC (previous 777D: 3PR) - Empty weight: 80160 kg (176722 lbs.) - Load carrying capacity: 90.9 metric tons (100 tons) - Gross Machine Weight (GMW): 161028 kg (355000 lbs.) - Length: 9.78 m (32.1 ft.) - Width: 5.53 m (18.2 ft.) - Height: 5.00 m (16.4 ft.) - Body Up Height: 9.95 m (32.7 ft.) - Maximum ground speed at 1900 engine rpm: 63.7 km/h (39.5 mph)

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• Hydraulic tank group: - Hoist, brake and torque converter hydraulic tank - Transmission hydraulic tank • Service/retarder air tanks, front brake master cylinder and brake makeup tank • Transmission/Chassis Electronic Control System

• Brake Electronic Control System

Shown is the left side of a 777D Update truck. The hydraulic tank group is visible. The hydraulic tank group consists of two separate tanks: the hoist, brake and torque converter hydraulic tank (front) and the transmission hydraulic tank (rear). The transmission hydraulic system is separated from all of the other hydraulic systems. The service/retarder air tanks, the front brake master cylinder, and the brake oil makeup tank are located on the hydraulic tank group. The second generation Electronic Programmable Transmission Control (EPTC II) has been replaced with the Transmission/Chassis Electronic Control System. The Transmission/Chassis Electronic Control Module (ECM) controls the same functions as the EPTC II plus the hoist and some other functions. The Automatic Retarder Control (ARC) and the Traction Control System (TCS) control modules have been replaced with one Brake System ECM. The Brake System ECM controls both the ARC and the TCS functions. The TCS is now connected to the CAT Data Link and the Electronic Technician (ET) service tool can be used to diagnose the TCS.

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• Folded-core radiator

Shown is the front of a 777D Update truck. The 777D Update truck uses a folded core radiator. The folded core style radiator provides the convenience of repairing or replacing smaller individual cores.

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• Truck body options: - 12 degree flat floor

Shown is the rear of a 777D Update truck. Two body options are available for the 777D Update truck:

- Dual-slope

- A 12 degree flat floor design that provides uniform load dumping, excellent load retention and a low center of gravity. - A dual-slope design with a "V" bottom main floor to reduce shock loading, center the load and reduce spills. All internal wear surfaces of the truck bodies are made with 400 Brinell hardness steel. All attachment body liners are also made with 400 Brinell hardness steel. The external components of the bodies are made of steel with a yield strength of 6205 bar (90000 psi). • Rear suspension cylinders

The rear suspension cylinders absorb bending and twisting stresses rather than transmitting them to the main frame.

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777D MAINTENANCE ice 777D Serv re Procedu

WALK AROUND INSPECTION 5 MAINTENANCE • Read the Operation and Maintenance Manual

Before working on or operating the truck, read the Operation and Maintenance Manual thoroughly for information on safety, maintenance and operating techniques. Safety precautions and Warnings are provided in the manual and on the truck. Be sure to identify and understand all symbols before starting the truck. The first step to perform when approaching the truck is to make a thorough walk around inspection. Look around and under the truck for loose or missing bolts, trash build-up and for coolant, fuel or oil leaks. Look for indications of cracks. Pay close attention to high stress areas as shown in the Operation and Maintenance Manual.

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10 HOURS DAILY MAINTENCE CHECKS BATTERIES

STEERING OIL LEVEL

FUEL LEVEL AND DRAIN MOISTURE

PRIMARY FUEL FILTER DISCONNECT SWITCH SUSPENSION CYLINDER HEIGHT

ENGINE OIL LEVEL AIR FILTERS AND PRECLEANERS

REAR AXLE BREATHER

RADIATOR DEBRIS AND COOLANT LEVEL FAN BELTS AND ETHER CYLINDER WINDSHIELD WASHER LEVEL AIR TANK MOISTURE

BRAKE CYLINDER AND BREATHER

INSPECT FRAME FOR CRACKS AND BODY SUPPORT PADS CHECK FOR LEAKS AND TRASH BUILD-UP

WASH WINDOWS, CAB FRESH AIR FILTERS, SEAT BELT, INDICATORS, GAUGES, BRAKE TESTS, SECONDARY STEERING AND BACK-UP ALARM

TIRE INFLATION PRESSURE

SUSPENSION CYLINDER HEIGHT AND GREASE BREATHERS

WHEEL NUTS HOIST, CONVERTER AND BRAKE OIL LEVEL

TRANSMISSION OIL LEVEL

6 • Maintenance - 10 hours/daily

The following list identifies the items that must be serviced every 10 Hours or Daily. - Walk-Around Inspection: Check for loose or missing bolts, leaks, trash build-up and cracks in frame structures and body support pads - Tire condition and inflation pressure - Wheel nuts - Suspension cylinders - Primary fuel filter - Fuel level and moisture - Rear axle breather - Hoist, converter and brake oil - Transmission oil - Air tank moisture - Brake cylinders and breathers - Radiator - Fan belts - Ether cylinder - Steering system oil - Engine crankcase oil - Batteries - Air filters and precleaners - Windshield washer fluid level - Cab fresh air filters - Back-up alarm - Secondary steering - Seat belts - Brakes

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7 1. Front wheel bearing magnetic inspection plug - Check weekly 2. Front wheel bearing drain plug

The front wheel bearing oil level is checked and filled by removing the plug (1) in the center of the wheel bearing cover. The oil should be level with the bottom of the plug hole. The fill plug is a magnetic plug. Inspect the fill plug weekly for metal particles. If any metal particles are found, remove the wheel cover and inspect the bearings for wear. The oil is drained by removing the drain plug (2).

• Oil change interval is 500 hours

The service interval for changing the front wheel bearing oil is 500 hours.

• Use only TDTO oil

Use only Transmission Drive Train Oil (TDTO) with a specification of (TO-4) or newer. TDTO TO-4 provides increased lubrication capability for bearings.

• Tire inflation

Check the tire inflation pressure. Operating the truck with the wrong tire inflation pressure can cause heat build-up in the tire and accelerate tire wear. NOTE: Care must be taken to ensure that fluids are contained while performing any inspection, maintenance, testing, adjusting and repair of the machine. Be prepared to collect the fluid in suitable containers before opening any compartment or disassembling any component containing fluids. Refer to the "Tools and Shop Products Guide" (Form NENG2500) for tools and supplies suitable to collect and contain fluids in Caterpillar machines. Dispose of fluids according to local regulations and mandates.

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• Front suspension cylinder charge

Check the front suspension cylinders for leaks or structural damage. Check the charge condition of the front suspension cylinders when the truck is empty and on level ground. Measure the charge height of the suspension cylinders and compare the dimension with the dimension that was recorded the last time the cylinders were charged. Recharge the cylinders with oil and nitrogen if necessary.

• Grease outlet fitting

A grease outlet fitting is located on one side of each front suspension cylinder. The grease supply fitting (arrow) is located on the opposite side of the suspension cylinder. No grease outlet fittings should be located on the same side of the suspension cylinder as the grease fill location. Having an outlet fitting on the same side of the suspension cylinder as the grease fill location will prevent proper lubrication of the cylinder.

• Grease supply fitting (arrow)

• Make sure grease flows from outlet fittings

Make sure that grease is flowing from the outlet fittings to verify that the suspension cylinders are being lubricated and that the pressure in the cylinders is not excessive.

INSTRUCTOR NOTE: For more detailed information on servicing the suspension system, refer to the Special Instruction "Suspension Cylinder Servicing" (Form SEHS9411) and the Technical Instruction Module "769C - 793B Off-highway Trucks--Suspension System" (Form SEGV2599).

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1. Brake linings - Inspect for wear

2. Brake carrier guide pins - Inspect clearance 3. Brake disc

Inspect the brake linings (1) for wear. The thickness of the brake linings (not including carrier) must not be less than 3.15 mm (.125 in). Measure the lining at both ends because one end can wear more than the other. The clearance between the brake carrier guide pins (2) and the brake disc (3) must not be less than 1.5 ± 0.5 mm (.06 ± .02 in.).

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1. Primary fuel filter (screen)

The primary fuel filter (screen) (1) is mounted behind the front engine mount on the right side of the engine. Inspect the condition of the screen at regular intervals. A plugged screen may cause low power or prevent the engine from starting.

2. Engine oil level low switch

An engine oil level switch (2) provides input signals to the Engine ECM. The Engine ECM provides an input signal to the Caterpillar Monitoring System, which warns the operator when the engine oil level is low and it is unsafe to operate the truck. Operating the truck with low engine oil may cause damage to the engine. The ENGINE OIL LEVEL LOW message is a Category 2 or 3 Warning.

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• Jacket water coolant S•O•S tap

Jacket water coolant samples can be taken at the Scheduled Oil Sampling (S•O•S) coolant analysis tap (arrow). The tap is located behind the jacket water pump on the right front of the engine.

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1. Transmission charging filter 2. Transmission oil S•O•S tap 3. Transmission oil filter bypass switch

Located behind the right front tire is the transmission charging filter (1). Transmission oil samples can be taken at the Scheduled Oil Sampling (S¥O¥S) tap (2). An oil filter bypass switch (3) is located on the filter. The oil filter bypass switch provides input signals to the Caterpillar Monitoring System, which informs the operator if the filter is restricted.

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13 • Fuel tank 1. Fuel level sight gauge • Fuel level sender

The fuel tank is located on the right side of the truck. The fuel level sight gauge (1) is used to check the fuel level during the walk around inspection. A fuel level sender is located on the fuel level sight gauge. The fuel level sender provides input signals to the Caterpillar Monitoring System, which informs the operator of the fuel level.

2. Condensation drain valve

Open the drain valve (2) to remove condensation from the fuel tank.

3. Fuel tank breather 4. Fuel cap vent

Inspect the condition of the fuel tank breather (3) and the fuel cap vent (4) at regular intervals.

5. Quick service fuel fill connector

Fuel can be added at the attachment quick service fuel fill connector (5).

• Fuel information

The percentage of sulfur in the fuel will affect the engine oil recommendations. The following is a summary of fuel sulfur and oil recommendations: 1. Use API CH-4 performance oils. 2. With fuel sulfur below 0.5%, any API CH-4 oils will have a sufficient Total Base Number (TBN) for acid neutralization. 3. For fuel sulfur values above 0.5%, the new oil TBN should be a minimum of 10 times the fuel sulfur. 4. When 10 times the fuel sulfur exceeds the oil TBN, reduce the oil change interval to about 1/2 the normal change interval.

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• Rear brake cylinder

Shown is the rear brake cylinder. The rear brake cylinder is located at the right inner frame to the right of the transmission group. The front brake cylinder is located behind the hydraulic tank group.

1. Brake cylinder breather

Inspect the condition of the breathers (1) for the brake cylinders. Oil should not leak from the breather. Oil leaking from the breather indicates that the oil piston seals in the brake cylinder needs replacement. Air flow from the breather during a brake application indicates that the brake cylinder air piston seal needs replacement.

2. Brake overstroke switch

If air is in the system or a loss of oil downstream from the cylinders occurs, the piston in the cylinder will overstroke and cause an indicator rod to extend and open the brake overstroke switch (2). The switch provides an input signal to the Caterpillar Monitoring System, which informs the operator of the condition of the service/retarder brake oil circuit. If an overstroke condition occurs, the problem must be repaired and the indicator rod pushed in to cancel the warning. NOTE: The front brake cylinder does not have an overstroke switch.

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15 • Final drives 1. Final drive magnetic inspection plug

2. Drain plug

• Check magnetic plugs for metal - Check weekly • Use only TDTO oil

The rear axles are equipped with planetary-type final drives. Rotate the final drive until the cover and plug are positioned as shown. The final drive oil level is checked and filled by removing the magnetic plug (1). The oil should be level with the bottom of the plug hole. Fill the rear axle housing with oil before filling the final drives with oil. Allow enough time for the oil to settle in all of the compartments. This can be as much as 20 minutes during cold temperatures. The oil is drained by removing the drain plug (2). The magnetic inspection plugs should be removed weekly from the final drives and checked for metal particles. For some conditions, checking the magnetic plugs is the only way to identify a problem which may exist. Use only Transmission Drive Train Oil (TDTO) with a specification of TO-4 or newer. TDTO TO-4 oil provides: - Maximum frictional capability required for gears. - Increased lubrication capability for bearings.

NOTICE • Flush all axle components after a failure

The rear axle is a common sump for the differential and both final drives. If a final drive or the differential fails, the other final drive components must also be checked for contamination and then flushed. Failure to completely flush the rear axle after a failure can cause a repeat failure within a short time.

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1. Differential magnetic inspection plug

Check the differential oil level by removing the magnetic inspection plug (1). The oil should be level with the bottom of the fill plug opening.

• Rear suspension cylinders

Inspect the rear suspension cylinders for leaks or structural damage. Check the charge condition of the rear suspension cylinders when the truck is empty and on level ground. Measure the charge height of the suspension cylinders, and compare the dimension with the dimension that was recorded the last time the cylinders were charged. Recharge the cylinders if necessary.

2. Rear axle breather

Inspect the condition of the rear axle breather (2) at regular intervals. The breather prevents pressure from building up in the axle housing. Excessive pressure in the axle housing can cause brake cooling oil to leak through the Duo-Cone seals in the wheel brake assemblies.

INSTRUCTOR NOTE: For more detailed information on servicing the suspension system, refer to the Special Instruction "Suspension Cylinder Servicing" (Form SEHS9411) and the Technical Instruction Module "769C - 793B Off-highway Trucks--Suspension System" (Form SEGV2599).

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• Body up retaining pins (arrow)

The body up retaining pins (arrow) are stored below the rear of the body. When work is to be performed while the body is raised, the body up retaining pins must be installed through the pin holes in the body and the rear frame to hold the body in the raised position. WARNING

The space between the body and the frame becomes a zero clearance area when the body is lowered. Failure to install the body up pins can result in injury or death to personnel working in this area.

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1. Transmission hydraulic tank 2. Hoist, converter and brake hydraulic tank

Shown are the transmission hydraulic tank (1) and the hoist, converter and brake hydraulic tank (2). Both tanks are equipped with oil level sight gauges. The oil level of both hydraulic tanks should first be checked with cold oil and the engine stopped. The level should again be checked with warm oil and the engine running.

3. Lower sight gauge for oil level with raised cylinders

The lower sight gauge (3) on the hoist, converter and brake hydraulic tank can be used to fill the tank when the hoist cylinders are in the RAISED position. When the hoist cylinders are lowered, the hydraulic oil level will increase. After the hoist cylinders are lowered, check the hydraulic tank oil level with the upper sight gauge.

4. Hoist, converter and brake tank breather

Inspect the hoist, converter and brake hydraulic tank breather (4) and the transmission hydraulic tank breather (5) for plugging.

5. Transmission tank breather • Inspect hydraulic tank cap vents 6. Service/retarder brake air tank drain valve

Inspect the condition of both hydraulic tank fill cap vents at regular intervals. The service/retarder brake air tanks are located on top of the hydraulic tank. Drain the moisture from the tanks daily with the drain valve (6).

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When filling the hydraulic tanks after an oil change, fill the tanks with oil to the FULL COLD mark on the sight gauge. Turn on the engine manual shutdown switch (see Slide No. 23) so the engine will not start. Crank the engine for approximately 15 seconds. The oil level will decrease as oil fills the hydraulic systems. Add more oil to the tanks to raise the oil level to the FULL COLD mark. Crank the engine for an additional 15 seconds. Repeat this step as required until the oil level stabilizes at the FULL COLD mark. Turn off the engine manual shutdown switch and start the engine. Warm the hydraulic oil. Add more oil to the tank as required to raise the oil level to the FULL WARM mark.

• Use only TDTO oil

In both tanks, use only Transmission Drive Train Oil (TDTO) with a specification of TO-4 or newer. TDTO TO-4 oil: - Provides maximum frictional capability required for clutch discs used in the transmission, torque converter and brakes. - Increases rimpull because of reduced slippage. - Increases brake holding capability by reducing brake slippage. - Controls brake chatter. - Provides maximum frictional capability required for gears.

NOTICE Failure to correctly fill the hydraulic tanks after an oil change may cause component damage.

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1. Parking brake release filter 2. Torque converter charging filter 3. Hoist, converter and brake oil S•O•S tap 4. Air dryer

Located in front of the hydraulic tanks are the parking brake release filter (1) and the torque converter charging filter (2). Hoist, converter and brake oil samples can be taken at the Scheduled Oil Sampling (S¥O¥S) tap (3). The air dryer (4) is located behind the left front tire. Inspect for oil spray around the air dryer. Oil spray can indicate that a problem exists in the air compressor.

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• Engine oil filters 1. Engine oil pressure sensor

• Oil filter restriction

The engine oil filters are located on the left side of the engine. The engine lubrication system is equipped with two oil pressure sensors (1). A sensor is located on each end of the oil filter base. One sensor measures engine oil pressure before the filters. The other sensor measures oil pressure after the filters (sensor shown). The sensors provide input signals to the Engine ECM. The ECM provides input signals to the Caterpillar Monitoring System, which informs the operator of the engine oil pressure. Together, these sensors inform the operator if the engine oil filters are restricted.

2. Trapped engine oil drain

The oil filter base also has a fitting (2) that can be used to drain the engine oil that is trapped above the filters. Do not add oil through the fitting because unfiltered oil will enter the engine. Any contamination could cause damage to the engine.

3. Aftercooler coolant S•O•S tap

Aftercooler coolant samples can be taken at the Scheduled Oil Sampling (S•O•S) coolant analysis tap (3). The tap is located behind the aftercooler water pump on the left front of the engine.

NOTICE When changing the engine oil filters, drain the engine oil that is trapped above the oil filters through the fitting (2) to prevent spilling the oil. Oil added to the engine through the fitting will go directly to the main oil galleries without going through the engine oil filters. Adding oil to the engine through the fitting may introduce contaminants into the system and cause damage to the engine.

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1. Engine oil S•O•S tap 2. Engine oil pressure sensor

Engine oil samples can be taken at the Scheduled Oil Sampling (S•O•S) tap (1) located on front of the oil filter base. Also shown is the engine oil pressure sensor (2) that measures the engine oil pressure before the filters.

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• Secondary fuel filters 1. Fuel priming pump 2. Fuel filter bypass switch

The secondary fuel filters and the fuel priming pump (1) are located above the engine oil filters on the left side of the engine. The fuel priming pump is used to fill the filters after they are changed. A fuel filter bypass switch (2) is located on the filter base. The bypass switch provides an input signal to the Engine ECM. The Engine ECM sends the signal to the Caterpillar Monitoring System, which informs the operator if the filters are restricted. NOTE: If the fuel system requires priming, it may be necessary to block the fuel return line during priming to force the fuel into the injectors.

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• Manual engine shutdown switch (arrow)

Before climbing the truck ladder, make sure that the manual engine shutdown switch (arrow) is OFF. The engine will not start if the manual shutdown switch is ON. If necessary, the switch can be used to stop the engine from the ground level.

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• Inspect radiator

While climbing the ladder, make a thorough inspection of the radiator. Be sure that no debris or dirt is trapped in the radiator cores.

• Battery disconnect switch (arrow)

The battery disconnect switch (arrow) is located under a cover on the front bumper near the right access ladder. If the machine is being parked for an extended period (overnight, etc.) turn off the disconnect switch and remove the key.

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• Batteries

The batteries are located on the right platform. Inspect the battery connections for corrosion or damage. Keep the battery terminals clean and coated with petroleum jelly. Inspect the electrolyte level in each battery cell, except maintenance free. Maintain the level to the bottom of the fill openings with distilled water.

WARNING Batteries give off flammable fumes that can explode resulting in personal injury. Prevent sparks near batteries. They could cause vapors to explode. Do not allow jump cable ends to contact each other or the machine. Do not smoke when checking battery electrolyte levels. Electrolyte is an acid and can cause personal injury if it contacts skin or eyes. Always wear eye protection when starting a machine with jumper cables. Always connect the battery positive (+) to battery positive (+) and the battery negative (-) to stalled machine frame (-).

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• Engine cooling systems: - Jacket water cooling system - Aftercooler cooling system 1. Jacket water coolant sight gauge 2. Aftercooler coolant sight gauge 3. Cooling system relief valves

The cooling system on the 777D Update trucks is divided into two systems. The two systems are the jacket water cooling system (right side) and the aftercooler cooling system (left side). These two systems are not connected. When servicing the cooling systems, be sure to drain and fill both systems separately. The two coolant levels are checked with the jacket water coolant sight gauge (1) and the aftercooler coolant sight gauge (2). Coolant is added by removing the respective radiator cap. The jacket water and the aftercooler cooling systems each have their own relief valve (3). If a cooling system overheats or if coolant is leaking from a relief valve, clean or replace the relief valve.

• Use distilled water

The water used in the cooling system is critical for good cooling system performance. Use distilled or deionized water whenever possible to prevent acids or scale deposits in the cooling system. Acids and scale deposits result from contaminants that are found in most common water sources.

• Never use water alone

Never use water alone. All water is corrosive at engine operating temperatures without coolant additives. Also, water alone has none of the lubrication properties which are required for water pump seals.

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• Trucks are filled with Extended Life Coolant (ELC)

The trucks are filled at the factory with Extended Life Coolant (ELC). If ELC is maintained in the radiator, it is not necessary to use a supplemental coolant additive. If more than 10% of conventional coolant is mixed with the ELC, a supplemental coolant additive is required.

• Conventional coolant:

• With conventional coolant, maintain a 3 - 6% concentration of supplemental coolant additive. - Too much additive will form insoluble salts that cause water pump seal wear, plugging and will coat parts with excessive deposits that prevent heat transfer. - Not enough additive will result in severe cavitation erosion which will pit and corrode cylinder liner and block surfaces. - Use the 4C9301 Test Kit to measure the concentration of the supplemental coolant additive in the cooling system.

- Maintain 3 - 6% concentration of supplemental coolant additive

• Maintain 30 - 60% Caterpillar Antifreeze concentration

• Maintain a 30 - 60% concentration of Caterpillar Antifreeze. - More than 60% antifreeze concentration will reduce freeze protection and cause radiator plugging. - Less than 30% antifreeze concentration will result in cavitation erosion which will pit and corrode cylinder liner and block surfaces and decrease water pump life. - Most commercial antifreezes are formulated with high silicate content for gasoline engines and are not recommended for diesel engines.

• Maintain correct operating temperature

• The engine should operate between 88 and 99°C (190 and 210°F). - Operating below this temperature range will cause overcooling problems. - Operating above this temperature range will cause overheating problems.

• Maintain correct cooling system pressure

• Cooling system pressure should be between 55 and 110 kPa (8 and 16 psi). - Raising the pressure raises the boiling point. If the pressure is inadequate, the coolant will boil over and the engine will overheat.

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• Do not fill cooling system too fast

• Do not fill the cooling system faster than 20 l/min. (5 gpm). - Filling the cooling system faster than 20 l/min. (5 gpm) will cause air pockets that could produce damaging steam.

• Adjust fan belts

• Keep fan belts adjusted.

• Keep radiator fins straight and clean

• Keep radiator cooling fins straight and clean.

4. Ether cylinder (not shown)

If the truck is equipped with an ether start system, the ether cylinder (4) (not shown) is located in the engine compartment behind the radiator. Make sure the ether cylinders are not empty.

• ET can turn ether system ON or OFF

A laptop computer with the Electronic Technician (ET) software installed can be connected to the machine to turn the ether injection system ON or OFF.

• Automatic ether injection

The Engine ECM will automatically inject ether from the ether cylinder during cranking. The duration of automatic ether injection depends on the jacket water coolant temperature. The duration will vary from 10 to 130 seconds.

• Manual ether injection

The operator can also inject ether manually with the ether switch in the cab on the center console (see Slide No. 46). The manual ether injection duration is 5 seconds. Ether will be injected only if the engine coolant temperature is below 10°C (50°F) and engine speed is below 1900 rpm. Ether starting tip: - Cold weather causes rough combustion and white exhaust smoke from unburned fuel. Ether injection will reduce the duration and severity of unburned fuel symptoms.

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4

5 1 2 3

27

• Steering system tank

The steering system tank is located on the right platform

1. Steering system oil level sight gauge

Check the steering system oil level at the sight gauge (1).

2. Steering system oil filter

The steering system oil filter (2) is located on the side of the steering tank.

3. Case drain oil filter

The steering system uses a pressure compensated piston type pump. Case drain oil from the steering pump returns to the steering tank through a case drain filter (3) on the side of the steering tank.

4. Steering tank pressure release button and breather

Before removing the cap to add oil to the steering system, depress the pressure release button (4) on the breather to release any remaining pressure from the tank.

5. Steering system S•O•S tap

Steering system oil samples can be taken from the Scheduled Oil Sampling (S•O•S) tap (5) located in the case drain return hose.

• Filter bypass valves

The steering system filter base and the case drain filter base have bypass valves that allow the steering oil to bypass the filters if they are plugged.

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1

2

28 • Engine air intake system components: 1. Air filter restriction indicators • Alert indicator on dash

Shown are the air intake system components. Check the air filter restriction indicators (1). If the yellow pistons are in the red zone (indicating that the filters are plugged), the air filters must be serviced. An air filter restriction indicator is also located on the dash (see Slide No. 47). The alert indicator lights when the filter restriction is approximately 6.2 kPa (25 in. of water).

2. Dust valves

Located next to the air filter housings are the precleaners. Check the dust valves (2) for plugging. If necessary, disconnect the clamp and open the cover for additional cleaning. Replace the dust valve if the rubber is not flexible.

• Replace dust valve if not flexible

The dust valve is OPEN when the engine is OFF and closes when the engine is running. The dust valve must be flexible and close when the engine is running or the precleaner will not function properly and the air filters will have a shortened life.

• Large primary element

Two filter elements are installed in the filter housings. The large element is the primary element and the small element is the secondary element.

• Small secondary element

Air intake system tips: - The primary element can be cleaned a maximum of six times. - Never clean the secondary element for reuse. Always replace the secondary element. - Air filter restriction causes black exhaust smoke and low power.

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1 2

29

1. Engine oil level dipstick 2. Engine oil fill tube

Located below a small cover on the engine hood is the engine oil level dipstick and the engine oil fill tube. Check the engine oil level with the dipstick (1) and add engine oil at the fill tube (2). Use only Diesel Engine Oil (DEO) with a specification of CF-4 or newer. DEO oil with a CH-4 specification is available and should be used if possible.

• Engine oil (DEO CH-4) - Higher temperature capability - Better soot control - Handles higher sulfur fuels

CH-4 engine oil: - Requires more performance tests than previous oils, such as CE or CF, and has a narrower performance band. - Can withstand higher temperatures before coking and has better dispersing capability for controlling soot. - Has better fuel sulfur neutralization capability.

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1

2

30 1. Parking/secondary brake air tank drain valve

A small air tank (not visible) is located behind the cab (see Slide No. 171). The air tank behind the cab supplies air to the parking and secondary brakes. Drain the moisture from the tank daily with the drain valve (1).

2. Windshield washer fluid reservoir

Check the fluid level of the windshield washer reservoir (2).

NOTE: Check the level of all oil compartments again with the engine running after the oil reaches the normal operating temperature.

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31

• Air conditioner filter (arrow)

The air conditioner filter (arrow) is located in a compartment in front of the cab. Clean or replace the filter element when a reduction of circulation in the cab is noticed.

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32

• 10 hours/daily checks performed in the operator's cab

The remaining 10 Hours or Daily checks are performed in the operator's compartment: - Brakes: Check operation - Indicators and gauges: Test operation - Seat belt: Inspect - Back-up alarm: Test operation - Secondary steering: Test operation The brakes are checked by engaging one of the brake systems and placing the shift lever in FIRST FORWARD. Accelerate the engine until the truck moves. The truck must not move below 1200 rpm. This procedure should be repeated for each brake lever or pedal.

• Cab fresh air filter (arrow)

The cab fresh air filter (arrow) is located behind the cover in the right front corner of the cab. Clean or replace the cab fresh air filter when necessary. INSTRUCTOR NOTE: Refer to the Operation and Maintenance Manual for information on the remaining tests performed in the cab.

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33

OPERATOR'S STATION • 777D Update cab resembles smaller "D" Series

The operator's station for the 777D Update Off-highway Trucks has been changed to improve operator comfort and ergonomics. The 777D Update cab now resembles the cab used on the smaller "D" Series Off-highway Trucks.

• TPMS external loading lamps (arrow)

The Truck Production Management System (TPMS) on the 777D Update Trucks is controlled by a separate ECM and is not on the Cat Data Link. There are two sets of TPMS external loading lamps on the truck. One set of lamps is on the left side of the cab (arrow) and the other set is on the right platform. The lamps are green and red. The lamps inform the loader operator of the loading progress toward a target payload weight. The lamps are active only during the loading cycle and are off at all other times.

- Green and red

• TPMS loading lamp operation

During loading, the green (continue loading) lamps will be ON until the payload is 95% of the target weight setting. Then, the red (stop loading) lamp will light. A "last pass" indication can be programmed into the system. With last pass indication, the TPMS calculates an average loader pass size and predicts payload weight. If the predicted weight after the NEXT loader pass will be above 95% of the target weight setting, the red lamps FLASH. The red lamps will be ON continuously after the last pass (when fully loaded). A minimum of three loader passes are required for the "last pass" indication option to function correctly.

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34

• Operator and trainer seats

Shown is a view of the operator's seat and the trainer's seat. The seats are more comfortable with improved seat adjustments.

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3

4

5 1 2

35

Machine Controls • Front panel components:

Located on the left side of the front panel are:

1. Telescopic/tilt steering column adjustment lever

- Telescopic/tilt steering column adjustment lever (1): Push for telescoping and pull for tilt.

2. Intermittent wiper/washer, turn signal and dimmer control

- Intermittent wiper/washer, turn signal control and dimmer switch (2)

3. Horn control

- Cigarette lighter (4): The cigarette lighter socket receives a 24-Volt power supply. This socket can be used as a power supply for 24-Volt appliances. A 12-Volt power port is provided behind the operator's seat.

4. Cigarette lighter 5. Front brake ON/OFF switch--caliper disc front brakes only

- Steering wheel mounted electric horn control (3)

- Front brake ON/OFF switch (5): (caliper disc front brakes only) When this switch is in the OFF position, the front brakes will NOT ENGAGE when the operator uses the service brake pedal.

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36

Shown is a closer view of the intermittent wiper/washer, turn signal control and dimmer switch. • Windshield washer

Windshield washer: Push the button at the end of the lever to activate the electrically powered windshield washer.

• Intermittent wiper

Intermittent wiper switch (six positions): - OFF (0) - Intermittent position 1 (one bar) - Intermittent position 2 (two bars) - Intermittent position 3 (three bars) - Low speed continuous wiper (I) - High speed continuous wiper (II)

• Dimmer switch

Dimmer switch: Pull the lever toward the operator for BRIGHT lights, and push the lever away from the operator for DIM lights.

• Turn signals

Turn signals: Lift the lever for a RIGHT turn, and lower the lever for a LEFT turn.

• Power window switch

A power window switch is mounted on the door as seen to the left of the steering wheel.

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37

• Retarder lever (black): - Caliper disc front-engages rear only - Oil cooled front-engages front and rear

Located on the right side of the steering column is the retarder lever (black). The retarder lever is used to modulate engagement of the service brakes. The retarder lever engages only the rear brakes on trucks with caliper disc front brakes, but engages the front and rear brakes on trucks with the optional oil cooled front brakes. The retarder lever can control the modulation of the service brakes more precisely than the service brake pedal located on the cab floor. Located on the dash to the right of the retarder lever are (from left to right):

• Key start switch

- Key start switch

• Temperature knob

- Temperature variable knob

• Fan speed switch

- Fan speed switch

NOTE: When the key start switch is turned to the crank position, if the Caterpillar Pre-Lubrication System is installed, a "P" will appear on the Caterpillar Monitoring System display during pre-lubrication. During engine cranking, if the ether starting aid is installed, an "E" will appear on the display during ether injection.

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1

2

3

4

38 1. Transmission shift lever 2. Parking brake air valve • Top and body up gear limits can be reprogrammed

3. Throttle pedal 4. Throttle position sensor

To the right of the operator's seat is the shift console which contains the transmission shift lever (1) and the parking brake air valve (2). The 777D Update truck has SEVEN speeds FORWARD and ONE REVERSE. The top gear limit and body up gear limit are programmable through the Transmission/Chassis ECM. The top gear limit can be changed from THIRD to SEVENTH. The body up gear limit can be changed from FIRST to THIRD. On the floor is the throttle pedal (3). A throttle position sensor (4) is attached to the throttle pedal. This sensor provides the throttle position input signals to the Engine ECM.

• Throttle position sensor supply voltage and output signal

The throttle position sensor receives a regulated 8.0 ± 0.5 Volts from the Engine ECM. The duty cycle output of the throttle position sensor should be 16 ± 6% at LOW IDLE and 85 ± 4% at HIGH IDLE.

• Elevated low idle reduced with parking brake or throttle pedal

The Engine ECM provides an elevated engine idle speed of 1300 rpm when the engine coolant temperature is below 60°C (140°F). The rpm is gradually reduced to 1000 rpm between 60°C (140°F) and 71°C (160°F). When the temperature is above 71°C (160°F), the engine will idle at LOW IDLE (700 rpm). Increasing the low idle speed helps prevent incomplete combustion and overcooling. To temporarily reduce the elevated idle speed, the operator can release the parking brake or depress the throttle momentarily, and the idle speed will decrease to LOW IDLE for 10 minutes.

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3 2

1

39

Located on the floor of the cab are: 1. Secondary brake pedal

- Secondary brake pedal (1): Used to modulate application of the parking brakes on the rear wheels and the service brakes on the front wheels.

2. Service brake pedal

- Service brake pedal (2): The service brake pedal is used to modulate engagement of the service brakes on all four wheels if the front brake ON/OFF switch is in the ON position (see Slide No. 35). For more precise modulation of the service brakes, use the manual retarder lever on the right side of the steering column.

3. Throttle pedal

- Throttle pedal (3): A throttle position sensor is attached to the throttle pedal. The throttle position sensor provides the throttle position input signals to the Engine ECM.

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40 • Hoist control lever (arrow) • Electronically controlled hoist system • Hoist SNUB position

The 777D Update truck hoist system is electronically controlled. The hoist control lever (arrow) activates the four positions of the hoist control valve. The four positions are: RAISE, HOLD, FLOAT and LOWER. A fifth position of the hoist valve is called the SNUB position. The operator does not have control over the SNUB position. The body up switch (see Slide No. 132) controls the SNUB position of the hoist valve. When the body is lowered, just before the body contacts the frame, the Transmission/Chassis ECM signals the hoist solenoids to move the hoist valve spool to the SNUB position. In the SNUB position, the body float speed is reduced to prevent hard contact of the body with the frame.

• Hoist lever in FLOAT for normal operation

The truck should normally be operated with the hoist lever in the FLOAT position. Traveling with the hoist in the FLOAT position will make sure the weight of the body is on the frame and body pads and not on the hoist cylinders. The hoist valve will actually be in the SNUB position.

• Reverse inhibitor operation

If the transmission is in REVERSE when the body is being raised, the hoist lever sensor is used to shift the transmission to NEUTRAL. The transmission will remain in NEUTRAL until: 1. The hoist lever is moved into the HOLD or FLOAT position; and 2. the shift lever has been cycled into and out of NEUTRAL.

• Starts a new TPMS cycle

The hoist lever is also used to start a new TPMS cycle. NOTE: If the truck is started with the body raised and the hoist lever in FLOAT, the lever must be moved into HOLD and then FLOAT before the body will lower.

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CATERPILLAR MONITORING SYSTEM 777D UPDATE OFF-HIGHWAY TRUCKS GAUGE CLUSTER MODULE

SPEED/TACH MODULE

1F

MESSAGE CENTER MODULE - GAUGES - MONITORING - WARNINGS - CLOCK SYNCHRONIZATION - MACHINE ID

ACTION LAMP

°C kPaMilesKM RPM Liter SERV CODE X10

...

ACTION ALARM

DISPLAY DATA LINK

INPUT COMPONENTS

SERVICE TOOL CAT DATA LINK BRAKE ECM (ARC) (TCS)

ENGINE ECM - EMISSIONS CONTROL - FUEL INJECTION - ETHER INJECTION - FAN CONTROL - ENGINE PRE-LUBE

- TRACTION ASSIST - RETARDING - OVERSPEED RETARDING - RETARDING LAMP RS232 LINK

TRANSMISSION/ CHASSIS ECM

- ICM CONTROL - NEUTRAL-START - BACK-UP ALARM - OVERSPEED PROTECTION - CTS - ENGINE PRE-LUBE - DIRECTIONAL SHIFT MANAGEMENT - AUTOLUBE

TPMS - TOP GEAR LIMIT - REVERSE NEUTRALIZE - LOAD COUNTER - NEUTRAL COAST INHIBIT - BODY UP GEAR LIMIT - STARTER PROTECTION - BODY HOIST CONTROL - SECONDARY STEERING - SPEED LIMITER

- PAYLOAD MEASUREMENT - STRUT DIAGNOSTICS

41 Caterpillar Monitoring System • Caterpillar Monitoring System

The Caterpillar Monitoring System is a flexible, modular monitoring system that includes: a message center module, various switches and sensors, an action lamp and action alarm. The "heart" of the system is the message center module where information is received from switches and sensors over the CAT Data Link and processed. The message center module then activates various output components.

• TPMS option is not on Data Link

The Truck Payload Measurement System (TPMS) is an optional system that can be installed on the trucks to monitor and record production data such as payloads and cycle times. The TPMS is not on the CAT Data Link and requires a separate communication port for downloading and viewing the production information.

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CATERPILLAR MONITORING SYSTEM

FOUR-GAUGE CLUSTER MODULE

SPEEDOMETER/ TACHOMETER MODULE

ACTION LAMP

OPERATOR MODE SCROLL SWITCH

TCS

15 10

ALERT INDICATORS

P

AUT

20

5

25 X100

R 24 V

MESSAGE CENTER MODULE

0

MPH km/h

41.4

30

SERV CODE

TCS

GROUND SPEED

ACTUAL GEAR

DISPLAY WINDOW

42 • Caterpillar Monitoring System

The Caterpillar Monitoring System includes: a four-gauge cluster module, a speedometer/tachometer module, a message center module, an action lamp and an action alarm. The message center module receives information from switches, sensors and other electronic controls on the machine through the CAT Data Link. The message center module processes this information and activates various output components. The output components could be in the four-gauge cluster module, the speedometer/tachometer module, the alert indicator or display window of the message center module, the action lamp and the action alarm. The display window shows the operator the condition of the machine systems and system diagnostic information.

• Warning categories:

The system has three Warning Categories. Category 1 alerts the operator of an abnormal machine condition by a gauge in the red zone and/or a flashing alert indicator. A Category 2 Warning will cause the action lamp to light in addition to the message center alert indicator. A Category 2 warning indicates that immediate operator action is necessary. Category 3 adds an action alarm, indicating that immediate machine shutdown is necessary.

- Category 1 - Category 2 - Category 3

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CATERPILLAR MONITORING SYSTEM

°C kPa Miles KM RPM Liter SERV

MESSAGE CENTER MODULE

CODE X10

INPUT COMPONENTS

CAT DATA LINK

HARNESS CODE PLUG

ELECTRONIC SERVICE TOOL

OPERATOR MODE SWITCH

ENGINE ECM

SERVICE SWITCH

BRAKE ECM TRANSMISSION/CHASSIS ECM

CLEAR SWITCH FUEL LEVEL SENDER

OUTPUT COMPONENTS

BRAKE OVERSTROKE SWITCH

GAUGE CLUSTER MODULE

TRANSMISSION FILTER SWITCH BRAKE OIL TEMP SENSOR

1F

TORQUE CONVERTER OIL TEMP SENSOR

SPEED/TACH MODULE

ACTION LAMP

ALTERNATOR R-TERMINAL BRAKE AIR PRESSURE

43 • Caterpillar Monitoring System - Inputs - Outputs

• Harness code plug

Shown is a diagram of the Caterpillar Monitoring System. Shown on the left are the components on the machine that provide inputs directly to the Message Center Module. The Message Center Module analyzes these inputs along with the inputs from the other ECM’s and sends output signals to the components shown on the right side of the diagram. The harness code consists of five pins in the Message Center Module 40-pin connector that can be either OPEN or GROUNDED. The combination of OPEN or GROUNDED pins determines which machine parameters the Message Center Module will perform. For example, if pins 3 and 12 are GROUNDED and pins 6, 16 and 22 are OPEN, that Message Center Module will function as a 777D Update Off-highway Truck. When connecting a laptop with ET software, ET will also automatically show this as a 777D Update Off-highway Truck.

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INSTRUCTOR NOTE: Some of the Caterpillar Monitoring System input and output components are shown during the discussion of other systems. See the following slide numbers: 43. Harness code plug 46. Operator mode switch 48. Service switch 48. Clear switch 13. Fuel level sender 180. Brake overstroke switch 112. Transmission filter switch 195 Brake oil temperature sensor 101. Torque converter oil temperature sensor 47. Alternator "R" terminal 170. Brake air pressure sensor 55. CAT Data Link/Electronic Service Tool 61. Engine ECM 196. Brake ECM 127. Transmission/Chassis ECM 44. Gauge cluster module 45. Speed/Tach module 44. Action lamp

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44

• Center front dash panel

Shown is the center of the front dash panel. Nine dash indicators, the four-gauge cluster module and the speedometer/tachometer module are visible.

• Left dash indicators (top to bottom):

The four dash indicators to the left of the four-gauge cluster module are (from top to bottom):

- Left turn

- Left turn

- Body up - Reverse - High beam

- Body up: Lights when the body is up. Input is from the body up switch. - Reverse: Lights when the shift lever switch is in REVERSE. - High beam

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• Right dash indicators (top to bottom) - Right turn

- 55 -

The five dash indicators to the right of the speedometer/tachometer module are (from top to bottom): - Right turn

- Action lamp - Secondary steering - Retarder - TCS

- Action lamp: Lights when a Category 2 or Category 3 Warning is active. - Secondary Steering: Lights when the secondary steering pump is ON. - Retarder: Lights when the retarder is ENGAGED (Auto or Manual). Flashes rapidly if a fault in the ARC system is detected. - TCS: Lights when the Traction Control System (TCS) is ENGAGED. Flashes rapidly if a fault in the TCS system is detected or when performing the TCS test.

• Four-gauge cluster module: - Engine coolant temperature - Brake oil temperature - System air pressure

The four parameters monitored by the four-gauge cluster module are (top then bottom, left to right): - Engine coolant temperature: Maximum operating temperature is 107°C (225°F). - Brake oil temperature: Maximum operating temperature is 124°C (255°F).

- Fuel level

- System Air Pressure: Minimum operating pressure is 483 kPa (70 psi). - Fuel Level: Minimum operating level is 8%.

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SPEEDOMETER/TACHOMETER MODULE 15 10

20

5

25 X100

0

MPH km/h

GROUND SPEED

30

ACTUAL GEAR

45 • Speed/tachometer module:

The three parameters monitored by the speedometer/tachometer module are:

- Tachometer - Ground speed - Actual gear

- Tachometer: Displays the engine speed in rpm. - Ground speed: Displayed in the left side of the three-digit display area and can be displayed in miles per hour (mph) or kilometers per hour (km/h). - Actual gear: Displayed in the right side of the two-digit display area and consists of two digits that show the actual transmission gear that is engaged. The left digit shows the actual gear (such as "1," "2," etc.). The right digit shows the direction selected ("F," "N" or "R").

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46

• Rocker switches (top row):

To the right of the speedometer/tachometer module are several rocker switches. The rocker switches control the following parameters:

- Lights - Automatic retarder control - Traction control system test - Operator Modes scroll

Top row (from left to right): - Lights - Vacant - ARC: Activates the Automatic Retarder Control (ARC) system. - TCS test: Tests the Traction Control System (TCS). Use this switch when turning in a tight circle with the engine at LOW IDLE and the transmission in FIRST GEAR. The brakes should ENGAGE and RELEASE repeatedly. The test must be performed while turning in both directions to complete the test. - Caterpillar Monitoring System operator scroll: Allows the operator to scroll through the Operator Modes in the message center module display window (see Slide No. 49).

STMG 721 01/00 • Rocker switches (bottom row): - Throttle back-up/ throttle lock - Ether starting aid - Air conditioning - Body up sound reduction - Secondary steering and parking brake release

- 58 -

Bottom row (from left to right): - Throttle back-up/throttle lock (customer installed option): Throttle back-up: Raises the engine speed to 1300 rpm if the throttle sensor signal is invalid. Throttle lock: If the transmission is in NEUTRAL and the parking brake is ENGAGED, the throttle lock will hold any current engine rpm selected by the operator. If any service or retarder brake is ENGAGED, the engine rpm will return to LOW IDLE. After a brake application, the throttle lock must be turned OFF to reset the system before the throttle lock function will work again. - Ether starting aid (customer installed option): Allows the operator to manually inject ether if the engine oil temperature is below 10°C (50°F) and engine speed is below 1900 rpm (see Slide No. 26). - Air conditioning - Body up sound reduction: Reduces the engine HIGH IDLE to 1800 rpm when the body is RAISED. - Secondary steering and parking brake release: Normally, when this switch is depressed, the steering system receives secondary steering oil and parking brake release oil flows to the tank. When the brake release diverter (towing) valve spool is shifted, this switch will also release the parking brakes (see Slide No. 187). NOTE: The secondary steering and parking brake release switch can also be used to provide hoist pilot oil for lowering the body on trucks with an inoperable engine (see Slide No. 160).

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47

• Message center module

To the right of the rocker switches is the message center module. The message center module contains ten alert indicators and a message display window.

• Alert indicators (top row):

The alert indicators on the message center module represent the following parameters:

- Engine oil pressure - Parking brake ON or rear brake master cylinder overstroke - Torque converter or brake oil temperature - Battery charging - Engine maintenance required

Top row (from left to right): - Engine oil pressure: The minimum operating pressure at low idle is 44 kPa (6.4 psi) and at high idle is 172 kPa (25 psi). - Parking brake ON or rear brake master cylinder overstroke. - Torque converter oil temperature or brake oil temperature: The maximum operating temperature is 124°C (255°F). - Battery charging: A Category 1 Warning is generated if the voltage on the message center Pin No. 1 is less than 23.8 or greater than 28.5 Volts. A Category 3 Warning is generated if the voltage is less than 22 or greater than 31 Volts. The minimum "R" terminal frequency is 90 Hz and 12.4 to 14.75 DC Volts. - Engine maintenance required: Low steering pressure, air filter restriction or low engine coolant flow.

STMG 721 01/00 • Alert indicators (bottom row): - Air filter restriction - Steering pressure low - Transmission oil filter restricted - Engine coolant flow low - Check engine

- 60 -

Bottom row (from left to right): - Air filter restriction: Maximum allowable restriction is 6.25 kPa (25 in. of water) - Low steering pressure - Transmission oil filter restricted: Maximum differential pressure is 250 kPa (36 psi). - Low engine coolant flow - Check engine: Lights only when active engine fault codes are present.

• Message display window

The message display window has a row of six digits, a decimal point between certain digits, six text symbols (units of measure), a x10 symbol and a service meter symbol that show machine system conditions and other service and setup information. The type of information shown on the screen depends on the message center operating mode.

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4 1

2

3

48

1. CAT Data Link connector

Shown is the circuit breaker panel located behind the operator's seat. A laptop computer with the Electronic Technician (ET) software installed can be connected to the CAT Data Link connector (1) to obtain diagnostic information and perform programming functions on all the electronic controls.

2. 12-Volt/5 amp power port

A 12-Volt/5 amp power port (2) provides a power supply for a laptop computer.

3. TPMS diagnostic connector

A laptop computer with the Truck Payload Measurement System (TPMS) software installed can be connected to the diagnostic connector (3) to obtain diagnostic and production information from the TPMS Electronic Control.

4. Service switches

Two service switches (4) are used to access the Caterpillar Monitoring System message center for stored diagnostic information. The switches are labeled with an "S" for SERVICE and a "C" for CLEAR. The Diagnostic Mode of the message center is changed by depressing and holding both service switches ("S" and "C"). When the desired mode is shown on the display, release the switches. By following the instructions in the Caterpillar Monitoring System Service Manual, the serviceman can program or diagnose faults in all electronic controls on the CAT Data Link.

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OPERATOR MODES INPUTS SERVICE METER MODE ODOMETER MODE

41.4

DIAGNOSTIC SCROLLING MODE

- ENGINE SPEED/TIMING SENSOR - ALTERNATOR "R" TERMINAL - ENGINE OIL PRESSURE

MILES or KM

- TRANSMISSION OUTPUT SPEED SENSOR

170

DIGITAL TACHOMETER MODE RESETTABLE LOAD COUNTER MODE

SERV CODE

RPM

- ENGINE SPEED/TIMING SENSOR

700 L

- BODY UP SWITCH (AFTER 10 SECONDS ACTIVATION) USE "C" SERVICE SWITCH TO CLEAR

74 027

SERV CODE

0709.05

MID

SERV CODE

End

CID FMI

49 • Message center module display window

The Caterpillar Monitoring System has 19 different possible modes of operation. Each mode provides important information regarding the condition of the machine and setup of the monitoring system. On the message center module display window, each mode is shown as a number. The mode of operation is changed using either the service switches located on the circuit breaker panel behind the operator or the Operator Mode scroll switch located on the dashboard. Only some modes are accessible to the operator by using the dashboard-mounted rocker switch in Mode 0. After the Caterpillar Monitoring System initially powers up, the message center display window will be in Mode 0. In Mode 0, the display window six-digit readout shows various machine system conditions to the operator. The digital readout normally shows the service meter. Using the Operator Mode scroll switch, the operator may scroll through the different Operator Modes. As the display scrolls, it will show the following information:

STMG 721 01/00 • Operator Modes: - Service Meter Mode - Odometer Mode - Digital Tachometer Mode - Resettable Load Counter Mode - Diagnostic Scrolling Mode

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Service Meter Mode: The message center module records the total number of operating hours. When in the Service Meter Mode, the six-digit readout shows the total machine operating hours. The service meter symbol is ON to indicate the display is functioning as a service meter. The operating hours will increase only when input signals are received from the engine speed/timing sensor, the alternator "R" terminal and the engine oil pressure sensor. If an Active Fault is present, SERV CODE will be displayed in the window. Odometer Mode: In this mode, the six-digit readout displays the total distance the machine has traveled. The units indicator will show MILES or KM, depending on the units of measure setting. The distance traveled will increase only when an input signal is received from the transmission output speed sensor. Digital Tachometer Mode: This mode displays the engine speed in revolutions per minute on the six-digit display. The units indicator shows rpm. The engine speed/timing sensor provides the input signal to the message center module. Resettable Load Counter Mode: Displays the number of loads since last re-set by the operator. The number of loads are calculated as equal to the number of times the body has been raised for more than ten seconds. The body up switch provides the input signals to the message center module. The load count can be cleared by depressing the "C" service switch located behind the operator's seat. Diagnostic Scrolling Mode: Using this mode, service personnel or the operator can view the faults the message center has detected. Faults CANNOT be placed on hold or cleared in this mode. SERV CODE will be displayed only if the fault is ACTIVE. Fault Codes consist of two parts: - Module Identification (MID): 030--Monitor, 036--Engine, 027--Transmission/Chassis, 116--Brake (ARC/TCS) - Component Identification (CID) and Failure Modifier (FMI)

NOTE: When the key start switch is turned to the crank position, if the Caterpillar Pre-Lubrication System is installed, a "P" will appear on the display during pre-lubrication. During engine cranking, if the ether starting aid is installed, an "E" will appear on the display during ether injection.

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SERVICE MODES HARNESS CODE MODE

-1-

NUMERIC READOUT MODE

-2-

SERV CODE

57

USE "S" SERVICE SWITCH TO SCROLL GAUGES

°C

°C

95

GA-1 (engine coolant) SERVICE MODE

kPa

88

-3-

715

GA-2 (brake oil)

027

---

SERV CODE

MID LOG MODE

UNITS MODE PERMANENT LOAD COUNT MODE DIAGNOSTIC AND PROGRAMMING MODE

LOG

-4-

-6-7-

KM

US L

0709.05 CID

SERV CODE

FMI

ALL GAUGES AND INDICATORS DISPLAY EXTREME CONDITIONS RECORDED

MILES

-5-

75

GA-3 (system air)

GA-4 (fuel) USE "S" SERVICE SWITCH TO SCROLL FAULTS USE "C" SERVICE SWITCH TO CLEAR FAULTS USE "C" SERVICE SWITCH TO CLEAR

USE "C" SERVICE SWITCH TO CHANGE UNITS

SI

1057 n

n

3 F

3FL

USE "S" SERVICE SWITCH TO SCROLL SUB-MODES

50 • Service Modes: - Harness Code Mode 1 - Numeric Readout Mode 2 - Service Mode 3 - Log Mode 4 - Units Mode 5 - Permanent Load Count Mode 6 - Diagnostic and Programming Mode 7

The service technician can use the message display to check other machine condition information by selecting the different modes available. Depress both service switches behind the operator's seat to scroll through the modes. Release the switches to enter a mode when its number is displayed. The seven Service Modes are described below. Harness Code Mode 1: This mode shows the machine model in which the monitoring system is installed. The earlier 769D through 777D Off-highway Trucks are all "34." The "D" Series Update truck harness codes are: 769D: "62" 771D: "61" 773D: "60" 775D: "59" 776D Update: "58"

777D Update: "57"

Numeric Readout Mode 2: This mode assists service personnel with troubleshooting sensor input signals. The Numeric Readout Mode more accurately shows the same information as shown on the gauges. The digital readout will display one gauge value at a time. To scroll through the four gauges, depress the "S" service switch and release the switch when the desired gauge number is displayed.

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• SERV CODE ON for active faults

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Service Mode 3: The message center module detects faults that occur with sensor and sender input signals and message center module output signals. The message center will then record the fault and turn on the SERV CODE indicator. If the fault goes away, the SERV CODE indicator is turned off. The fault code remains stored for future reference. This mode helps service personnel see and troubleshoot faults that the message center module has detected. Faults from other machine systems connected to the CAT Data Link are also shown in this mode.

• Action alarm sounds when fault is displayed

When a fault is displayed in the window, the action alarm will sound when the component or circuit changes state. For example, if the display shows the fault code for the torque converter temperature sensor and the technician unplugs and then plugs in the connector to the torque converter temperature sensor, the action alarm will sound if the message center module detects a change from an OPEN to a CLOSED circuit.

• Use "S" service switch to scroll faults

Use the "S" service switch to scroll through the logged faults. Use the "C" service switch to clear the logged faults that have been repaired.

• Use "C" service switch to clear faults • Log Mode indicates extreme conditions

Log Mode 4: The Log Mode is a management and maintenance tool which is useful for tracking machine history. The message center module records the extreme value for each machine condition being monitored. When in this mode, each gauge in the four-gauge cluster will display its highest or lowest recorded condition, and the speedometer and tachometer will display their highest recorded values. Alert indicators will also light when an abnormal condition has existed. Use the "C" service switch to clear the logged values. Mode 4 must also be exited before the logged values will be cleared from memory. Units Mode 5: This mode is used to toggle the ground speed display (mph/km/h) between U.S. and SI (metric) units of measure. Use the "C" service switch to change the units of measure. Permanent Load Count Mode 6: Displays the total number of loads accumulated since the machine was put into production. The number of loads are calculated as equal to the number of times the body has been raised for more than 10 seconds. This mode cannot be reset. Diagnostic and Programming Mode 7: The Caterpillar Monitoring System display for Mode 7 has been expanded to include several submodes to extend the diagnostic capabilities. After entering Mode 7, use the "S" service switch to scroll through the sub-modes. The operator scroll switch and the "C" service switch can also be used in some of the sub-modes.

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MODE 7 SUB-MODES USE "S" SERVICE SWITCH TO SCROLL SUB-MODES

MODES - 7.1 -

n

n

1 r

1 r

3 F

3F L

SHIFT MONITORING MODE

LEFT SIDE--SHIFT LEVER RIGHT SIDE--TRANSMISSION GEAR

- 7.2 - 7.3 - 7.4 - 7.5 -

RPM

T

1 8 3 4

C

- - - -

E

1 8 3 4

RPM

RPM

HL

0 H

TRANSMISSION OUTPUT SPEED (TOS) DISPLAY MODE TORQUE CONVERTER OUTPUT SPEED (COS) DISPLAY MODE ENGINE OUTPUT SPEED (EOS) DISPLAY MODE

HL

4 0 L

HL

USE OPERATOR SCROLL SWITCH TO TOGGLE FROM INPUT TO OUTPUT

8 0 R

HL 1 0 0 F

HO

0 S

HOIST DISPLAY MODE--SENSOR INPUT TO ECM or ECM OUTPUT TO SOLENOIDS

- 7.6 -

NEUTRAL

REVERSE

FIRST

SECOND

0 0 01 11

0 0 1 0 11

0 0 1 1 01

0 0 1 1 10

TRANSMISSION GEAR SWITCH INPUT MODE

- 7.7 -

- 7.8 -

OFF

ON

1 = OPEN 0 = GROUNDED ECONOMY SHIFT MODE

THIRD

J1 PINS

USE "C" SERVICE SWITCH TO TURN ON or OFF

REVERSE

NEUTRAL

FIRST

SECOND

0 0 0 1 11

0 0 10 11

0 0 1 1 01

0 0 1 1 10

TRANSMISSION SHIFT LEVER SWITCH INPUT MODE

0 1 0 0 11 36 33 32 31 30 29

1 = OPEN 0 = GROUNDED

THIRD

J1 PINS

0 1 0 0 11 23 27 19 35 24 14

51 7.1

Shift Monitoring Mode: Displays the position of the shift lever switch on the left of the display and the position of the transmission gear switch on the right of the display. The D6 digit will display "L" when the lockup clutch is ENGAGED. n 1 r 3 F --D1 D2

7.2

n 1 3 --D3 D4

r F -D5

L -D6

Shift lever n, actual gear n, lockup clutch RELEASED Shift lever 1R, actual gear 1R, lockup clutch RELEASED Shift lever 3F, actual gear 3F, lockup clutch ENGAGED Digital position on display

Transmission Output Speed (TOS) Display Mode: Displays the rpm of the TOS sensor. T --D1 D2

1 8 --D3 D4

3 -D5

4 -D6

TOS = 1834 rpm Digital position on display

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7.3

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Torque Converter Output Speed (COS) Display Mode: Displays the rpm of the COS sensor (if equipped). 777D Update trucks do not have a COS sensor. "_ _ _ _" will be displayed. C --D1 D2

7.4

3 -D5

4 -D6

COS = 1834 rpm Digital position on display

Engine Output Speed (EOS) Display Mode: Displays the rpm of the EOS sensor. E --D1 D2

7.5

1 8 --D3 D4

1 8 --D3 D4

3 -D5

4 -D6

EOS = 1834 rpm Digital position on display

Hoist Display Mode: Displays the hoist lever sensor input signal to the Transmission/Chassis ECM or the hoist lever output signal from the Transmission/Chassis ECM. The input and output signals can be different depending on the hoist lever strategy. For example, if a machine is started with the hoist lever in FLOAT, the hoist strategy will keep the body in HOLD until the lever is cycled from FLOAT to HOLD and then back to FLOAT. Therefore, the input signal can be FLOAT and the output signal will be HOLD. H H H H -D1

L L L L -D2

4 8 1 0 --D3 D4

0 0 0 0 -D5

H L R F -D6

Hoist lever in HOLD Hoist lever in 40% LOWER Hoist lever in 80% RAISE Hoist lever in 100% FLOAT Digital position on display

Depress the operator scroll switch and the above display changes to show the hoist output signal. The "L" changes to an "O" and the status of the hoist system is displayed in the same format. H H H H -D1

0 0 0 0 -D2

4 8 --D3 D4

0 0 0 0 -D5

H L R S -D6

Hoist output in HOLD Hoist output in 40% LOWER Hoist output in 80% RAISE Hoist output in SNUB Digital position on display

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7.6

Transmission Gear Switch Input Mode: Displays the transmission gear switch input signals to the Transmission/Chassis ECM. Transmission gear switch inputs correspond to Pins 29, 30, 31, 32, 33 and 36 in the J1 connector of the Transmission/Chassis ECM. If the particular input is grounded, a "0" will be displayed. If the input is not grounded (OPEN), a "1" will be displayed. A normal transmission gear position will have two of the five gear wires grounded along with the ground verify signal (Pin 36). Pin 36 should always be grounded, and a "0" should always be displayed in the D1 position of the display. Therefore, a correctly functioning transmission gear switch and harness should always have three 0's and three 1's for each gear position. 0 0 0 0 0 0 0 0 0 -D1 36

7.7

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0 0 0 0 1 1 1 1 1 -D2 33

0 1 1 1 0 0 0 1 1 -D3 32

1 0 1 1 0 1 1 0 0 -D4 31

1 1 0 1 1 0 1 0 1 -D5 30

1 1 1 0 1 1 0 1 0 -D6 29

Pins grounded in NEUTRAL: Pins grounded in REVERSE: Pins grounded in FIRST: Pins grounded in SECOND: Pins grounded in THIRD: Pins grounded in FOURTH: Pins grounded in FIFTH: Pins grounded in SIXTH: Pins grounded in SEVENTH:

32 and 33 31 and 33 30 and 33 29 and 33 31 and 32 30 and 32 29 and 32 30 and 31 29 and 31

Digital position on display Pin number in the J1 connector

Economy Shift Program Mode: (not available for 777D trucks) Displays whether the economy shift feature is ON or OFF. The operator can select between faster cycle times or better fuel economy. Turning this feature ON or OFF changes the torque map used by the engine control and the shift points used by the transmission control. ON is the ECONOMY Mode. OFF is the FULL POWER Mode. When the economy shift feature is ON, full power is still used in FIRST and SECOND Gears. The economy torque map is only used in gears THREE and up. Use the "C" service switch to turn this feature ON or OFF..

--D1 D2

O O --D3 D4

F N -D5

F -D6

Setting at OFF Setting at ON Digital position on display

NOTE: The 777D Update truck does not use the economy shift feature. On 777D Update trucks a "dash" will be shown in the display window in Mode 7.7. On 777D Update trucks the horsepower can be changed from 686 kW (920 hp) to 746 kW (1000 hp) by programming the Engine ECM with the ET service tool.

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7.8

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Transmission Shift Lever Switch Input Mode: Displays the transmission shift lever switch input signals to the Transmission/Chassis ECM. Transmission shift lever switch inputs correspond to Pins 14, 19, 24, 27, 35 and 23 in the J1 connector of the Transmission/Chassis ECM. If the particular input is grounded, a "0" will be displayed. If the input is not grounded (OPEN), a "1" will be displayed. A normal transmission gear position will have two of the five gear wires grounded along with the ground verify signal (Pin 23). Pin 23 should always be grounded and a "0" should always be displayed in the D1 position of the display. Therefore, a correctly functioning transmission shift lever switch and harness should always have three 0's and three 1's for each gear position. 0 0 0 0 0 0 0 0 0 -D1 23

0 0 0 0 1 1 1 1 1 -D2 27

0 1 1 1 0 0 0 1 1 -D3 19

1 0 1 1 0 1 1 0 0 -D4 35

1 1 0 1 1 0 1 0 1 -D5 24

1 1 1 0 1 1 0 1 0 -D6 14

Pins grounded in REVERSE: Pins grounded in NEUTRAL: Pins grounded in FIRST: Pins grounded in SECOND: Pins grounded in THIRD: Pins grounded in FOURTH: Pins grounded in FIFTH: Pins grounded in SIXTH: Pins grounded in SEVENTH: Digital position on display Pin number in the J1 connector

27 and 19 27 and 35 27 and 24 27 and 14 19 and 35 19 and 24 19 and 14 35 and 24 35 and 14

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1

2 3

52

1. TPMS Module 2. Transmission/ Chassis ECM

Located in the compartment at the rear of the cab are the Truck Payload Measurement System (TPMS) Module (1), the Transmission/Chassis ECM (2) and the Brake ECM (3).

3. Brake ECM

The TPMS is an optional system that can be installed on the trucks to keep track of production data such as payloads and cycle times. The TPMS is not on the Cat Data Link and requires a separate communication port for downloading and viewing the production information. The information from the TPMS control can be accessed through the Payload Operator Display (POD) or a laptop computer with the TPMS software. The Transmission/Chassis ECM controls the shifting of the transmission, torque converter lockup, the hoist system, the neutral-start feature, power train filter, temperature monitoring, and the secondary steering control. The Brake ECM controls the Automatic Retarder Control (ARC) system, and the Traction Control System (TCS). The Transmission/Chassis ECM, the Brake ECM, the Engine ECM and the Caterpillar Monitoring System communicate with each other through the CAT Data Link. All the information from these controls can be accessed through the Caterpillar Monitoring System message center or a laptop computer with Electronic Technician (ET) software.

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1

2 6 3

4 5

53

• Electrical components

Located in the compartment at the rear of the cab are several electrical components. Some of the electrical components are: - Wiper delay module (1) - Ether solenoid diode resister (2): When an ether solenoid is deenergized, an electrical charge can be generated that will travel back through the circuit. The electrical charge can be large enough to cause damage to other electrical components. The diode resister prevents the electrical charges from traveling backwards and causing damage. - Flasher relay (3) - Gauge panel dimmer module (4) - Engine oil prelube and backup alarm relays (5) - Headlamp brights, wipers and ether solenoid relays (6)

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1

2

54

• Electrical components

Other electrical components located at the rear of the cab are: - 5 amp/24 Volt to 12 Volt converter (1) - Secondary steering, hazard light and fog light relays (2)

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55

• Electronic Technician (ET)

Shown is the new generation Communication Adapter and a laptop computer with the Electronic Technician (ET) diagnostic software installed. The communication adapter is connected to the CAT Data Link diagnostic connector located on the circuit breaker panel.

• CAT Data Link

The CAT Data Link consists of a pair of twisted wires that connect to all of the Electronic Control Modules (ECM's) on a machine. The wires are twisted to reduce electrical interference from unwanted sources such as radio transmissions. All sensors and switches that provide an input to an ECM can be shared with other ECM's on the CAT Data Link. The ability to share the inputs eliminates the need for more than one sensor in the same system. A laptop computer with the Electronic Technician (ET) diagnostic software installed can also be connected to the CAT Data Link and see the information that is being transmitted between the ECM's.

• ECAP or ET must be used with electronic controls

The Transmission/Chassis ECM and Brake ECM (ARC and TCS) used on the 777D Update trucks do not have diagnostic windows to access diagnostic information. To perform diagnostic and programming functions in these ECM's, the service technician must use an ECAP or a laptop computer with the ET software installed.

• ET version 2.0 required for Brake ECM

ET version 2.0 or greater must be used to communicate with the Brake ECM.

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56 Truck Payload Measurement System (TPMS) • Payload Operator Display (POD)

• TPMS load cycle

Located above the operator is the Payload Operator Display (POD). The POD is installed on trucks with the attachment Truck Payload Measurement System (TPMS). TPMS is a management tool that monitors and records load cycles. A load cycle includes: - Load cycle number: Records a maximum of 1400 cycles. - Load cycle date: The date must be set with a laptop computer that has the TPMS software (Form SERD0032) installed. - Load cycle time: The time must be set with a laptop computer that has the TPMS software (Form SERD0032) installed. - Load weight - Empty travel time - Empty travel distance - Empty stopped time - Load time - Loaded stopped time - Loaded travel time

• POD switches, display window and LED's

Two switches are mounted on the POD. The left switch turns on the TPMS. No load cycles will be recorded if this switch is in the OFF position. The right switch is the test/set switch that is used to diagnose and program the TPMS while viewing the information in the display window. The Light Emitting Diodes (LED's) indicate when the truck is being loaded (green) and fully loaded (red).

• Hazard light switch

A hazard light switch is mounted to the right of the POD.

• TPMS set p with

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57

• TPMS setup with laptop computer

To set up the TPMS the first time, a laptop computer with the TPMS software (Form SERD0032) installed must be used to set the correct date and time. The laptop computer must also be used to set the "User Defined Data," which will appear on the top of all TPMS reports when they are printed. The User Defined Data can contain up to four lines of information with up to 10 numbers and/or letters on each line. All programming requirements and diagnostic troubleshooting can be done with the laptop computer.

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1

2

58

• TPMS setup with POD 1. Mode switch 2. Test/set switch

After the correct date, time and User Defined Data have been programmed with a laptop computer, the POD can also be used to perform some of the setup requirements and diagnostics. To program the TPMS with the POD, the POD must be removed to provide access to the mode switch (1). All the programming and diagnostic modes are listed on the decal. Depress the mode switch until the desired mode is displayed. When the desired mode is reached, the test/set switch (2) can be used to change the setting shown in the display window.

INSTRUCTOR NOTE: For more detailed information on the TPMS, refer to the Service Manual module "Truck Payload Measurement System With Real Time Clock--Systems Operation, Testing and Adjusting" (Form SENR4733).

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59

ENGINE • 3508B engine

Shown is the 3508B twin turbocharged and aftercooled engine used in the 777D Update Off-highway Truck.

• Engine specifications

The engine performance specifications for the 777D Update truck are: - Serial No. Prefix: 2GR - performance spec: 0K1144--1000 hp 0K1145--920 hp - max altitude: 2288 m (7500 ft.) - gross power: 746 kW (1000 hp) or 686 kW (920 hp) - full load rpm: 1750 - high idle rpm: 1937 - stall speed rpm: 1540 to 1670 These engines utilize the Electronic Unit Injection (EUI) system for power, reliability and economy with reduced sound levels and low emissions. NOTE: On the 777D Update truck, the horsepower can be changed from 686 kW (920 hp) to 746 kW (1000 hp) by programming the Engine ECM with the ET service tool.

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3500B ELECTRONIC CONTROL SYSTEM COMPONENT DIAGRAM

ENGINE ECM

GROUND BOLT

ELECTRONIC UNIT INJECTORS

MAIN KEY START 15 AMP POWER RELAY SWITCH BREAKER

THROTTLE POSITION SENSOR COOLANT TEMPERATURE AFTERCOOLER TEMPERATURE

DISCONNECT SWITCH 24 V

TIMING CALIBRATION CONNECTOR ENGINE OIL LEVEL SWITCH

SPEED/TIMING SENSOR ENGINE OIL PRESSURE (UNFILTERED)

ENGINE OIL PRESSURE (FILTERED) MANUAL ETHER AID SWITCH

ETHER AID RELAYS AND SOLENOID

ATMOSPHERIC PRESSURE THROTTLE OVERRIDE SWITCH TURBO OUTLET PRESSURE (BOOST)

FUEL FILTER BYPASS SWITCH

RIGHT TURBO INLET PRESSURE

LEFT TURBO INLET PRESSURE

RIGHT TURBO EXHAUST

GROUND LEVEL SHUTDOWN SWITCH CAT DATA LINK

CRANKCASE PRESSURE

SERVICE TOOL TRANSMISSION/CHASSIS ECM

A/C PRESSURE SWITCH

BRAKE ECM CATERPILLAR MONITORING SYSTEM SHUTTER SOLENOID

LEFT TURBO EXHAUST COOLANT FLOW SWITCH

PRE-LUBRICATION RELAY

60 Engine Electronic Control System • 3500B electronic control system component diagram

Shown is the electronic control system component diagram for the 3508B engines used in the 777D Update trucks. Fuel injection is controlled by the Engine Electronic Control Module (ECM). Many electronic signals are sent to the Engine ECM by sensors, switches and senders. The Engine ECM analyzes these signals and determines when and for how long to energize the injector solenoids. When the injector solenoids are energized determines the timing of the engine. How long the solenoids are energized determines the engine speed.

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• Personality module flash files

Occasionally Caterpillar will make changes to the internal software (personality module) that controls the performance of the engine. These changes can be performed by using the WinFlash program that is part of the laptop software program, Electronic Technician (ET). ET is used to diagnose and program the electronic controls used in Off-highway Trucks. If using the WinFlash program, a "flash" file must be obtained from Caterpillar and uploaded into the existing ECM personality module.

• 777D Update truck engine meets new emission regulations

The 777D Update truck engines are designed to meet the US Environmental Protection Agency (EPA) Tier I emissions regulations for engines over 560 gross kW (750 gross hp). To meet this regulation the 777D Update truck engine will use a new Emission Software. When installing the new Emission Software "flash" files in an Engine ECM, ET can use the American Trucking Association (ATA) Data Link or the CAT Data Link. The ATA and CAT Data Links consist of a pair of twisted wires that connect to the Engine ECM and the diagnostic connector in the cab. The wires are twisted to reduce electrical interference from unwanted sources such as radio transmissions.

• ATA or CAT Data Link used for flashing ECM

• Pull-up Voltage

The Engine ECM will provide a "Pull-up Voltage" to the signal circuit of most sensors when the ECM senses an OPEN circuit. Frequency sensors do not receive a Pull-up Voltage. The signal circuit is usually Pin C of the 3-pin sensor connectors. The Pull-up Voltage for most sensors is approximately 6.50 Volts, but this value can vary with different electronic controls. Generally, the Pull-up Voltage will be higher than the high value of a sensor's normal range. For example, the normal range of a coolant temperature sensor is 0.4 to 4.6 Volts with temperatures between -40¡C and +120¡C (-40¡F and +248¡F). The Pull-up Voltage of 6.50 Volts for this sensor is greater than the normal 4.6 Volts high value.

• Pull-up Voltage test

To test for Pull-up Voltage, use a digital multimeter set to "DC Voltage," and use the following procedure (key start switch must be ON): 1. Measure between Pin B (analog or digital return) and Pin C (signal) on the ECM side of a sensor connector before it is disconnected. The voltage that is associated with the current temperature or pressure should be shown. 2. Disconnect the sensor connector while still measuring the voltage between Pins B and C. If the circuit between the ECM and the sensor connector is good, the multimeter will display the Pull-up Voltage.

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INSTRUCTOR NOTE: Some of the 3508B Engine Electronic Control System input and output components are shown during the discussion of other systems. See the following slide numbers: 61. Engine ECM 61. Timing calibration connector 66. EUI injector 38. Throttle position sensor 72. Coolant temperature sensor 77. Aftercooler temperature sensor 81. Engine oil pressure sensor (filtered) 62. Atmospheric pressure sensor 93. Turbo outlet pressure sensor 90. Turbo inlet pressure sensor (right and left) 92. Turbo exhaust temperature sensors (right and left) 80. Engine oil level switch 46. Manual ether aid switch 86. Fuel filter bypass switch 65. Crankcase pressure sensor N/A. A/C pressure switch (not shown) 73. Coolant flow switch 63. Speed timing sensor 82. Engine oil pressure sensor (unfiltered) 53 and 26. Ether aid relays and solenoid 46. Throttle override switch 23. Ground level shutdown switch 55. CAT Data Link/Service Tool 127. Transmission/Chassis ECM 196. Brake ECM 41. Caterpillar Monitoring System N/A. Shutter solenoid (not shown) 53 and 69. Pre-lubrication relay and solenoid 67. User defined shutdown switch 60. ATA Data Link

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1 3

2

4

61 1. Engine ECM - Controls fuel injection - Controls other systems 2. J1 connector

Fuel injection and some other systems are controlled by the Engine ECM (1) located at the front of the engine. Other systems controlled by the Engine ECM are: ether injection, engine start function and engine oil pre-lubrication. The Engine ECM has two 40-pin connectors. The connectors are identified as "J1" (2) and "J2" (3) Be sure to identify which connector is the J1 or J2 connector before performing diagnostic tests.

3. J2 connector • ECM cooled by fuel 4. Timing calibration connector

The Engine ECM is cooled by fuel. Fuel flows from the fuel transfer pump through the ECM to the secondary fuel filters. A 2-pin timing calibration connector (4) is located next to the ECM. If the engine requires timing calibration, a timing calibration sensor (magnetic pickup) is installed in the flywheel housing and connected to the timing calibration connector. Using the Caterpillar ET service tool, timing calibration is performed automatically for the speed/timing sensors. The desired engine speed is set to 800 rpm. This step is performed to avoid instability and ensures that no backlash is present in the timing gears during the calibration process. Timing calibration improves fuel injection accuracy by correcting for any slight tolerances between the crankshaft, timing gears and timing wheel. Timing calibration is normally performed after the following procedures: 1. ECM replacement 2. Speed/timing sensor replacement 3. Timing wheel replacement

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62

• Atmospheric pressure sensor (arrow)

The atmospheric pressure sensor (arrow) is located adjacent to the Engine ECM. The Engine ECM uses the atmospheric pressure sensor as a reference for calculating boost and air filter restriction.

• High altitude derate

The sensor is also used for derating the engine at high altitudes. The ECM will derate the engine at a rate of 1% per kPa to a maximum of 20%. Derating begins at a specific elevation. The elevation specification can be found in the Technical Marketing Information (TMI) located in the Caterpillar Network. If the Engine ECM detects an atmospheric pressure sensor fault, the ECM will derate the fuel delivery to 20%. If the Engine ECM detects an atmospheric and turbocharger inlet pressure sensor fault at the same time, the ECM will derate the engine to the maximum rate of 40%. The Engine ECM also uses the atmospheric pressure sensor as a reference when calibrating all the pressure sensors.

• Atmospheric pressure sensor signal is DC Volts

The atmospheric pressure sensor is one of the many analog sensors that receive a regulated 5.0 ± .0.5 Volts from the Engine ECM. The atmospheric pressure sensor output signal is a DC Voltage output signal that varies between 0.2 and 4.8 Volts DC with an operating pressure range between 0 and 111 kPa (0 and 15.7 psi).

• Check atmospheric pressure sensor output signal

To check the output signal of analog sensors, connect a multimeter between Pins B and C of the sensor connector. Set the meter to read "DC Volts." The DC Voltage output of the atmospheric pressure sensor should be between 0.2 and 4.8 Volts DC.

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2

1

63

1. Engine speed/timing sensor

The engine speed/timing sensor (1) is positioned near the rear of the left camshaft. The sensor signals the speed, direction and position of the camshaft by counting the teeth and measuring the gaps between the teeth on the timing wheel which is mounted on the camshaft.

• No signal from speed/timing sensor will prevent engine operation

The engine speed/timing sensor is one of the most important inputs to the Engine ECM. If the Engine ECM does not receive an input signal from the engine speed/timing sensor, the engine will not run.

• Check speed/timing sensor output signal

The engine speed/timing sensor receives a regulated 12.5 ± 1.0 Volts from the Engine ECM. To check the output signal of the speed/timing sensor, connect a multimeter between Pins B and C of the speed/timing sensor connector. Set the meter to read "Frequency." The frequency output of the speed/timing sensor should be approximately: - Cranking: 23 to 40 Hz - Low Idle: 140 Hz - High Idle: 385 Hz

2. Engine speed sensor

A passive (two wire) engine speed sensor (2) is positioned on top of the flywheel housing. The passive speed sensor uses the passing teeth of the flywheel to provide a frequency output. The passive speed sensor sends the engine speed signal to the Transmission/Chassis ECM and the Brake ECM.

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The signal from the passive speed sensor is used for the Automatic Retarder Control (ARC) engine control speed. The output signal of the passive speed sensor can also be checked by connecting a multimeter between the two pins of the speed sensor connector and setting the meter to read frequency. NOTE: Turn ON the engine shutdown switch (see Slide No. 23) during the cranking test to prevent the engine from starting. The cranking speed and frequency output will vary depending on weather and machine conditions (battery charge). When viewing engine speed in the ET status screen, cranking speed should be between 100 and 250 rpm.

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64

• Throttle position sensor (arrow)

The throttle position sensor (arrow) provides the desired throttle position to the Engine ECM. If the Engine ECM detects a fault in the throttle position sensor, the throttle back-up switch (see Slide No. 46) can be used to increase the engine speed to 1300 rpm.

• Throttle position sensor signal is PWM

The throttle position sensor receives a regulated 8.0 ± 0.5 Volts from the Engine ECM. The throttle position sensor output signal is a Pulse Width Modulated (PWM) signal that varies with throttle position and is expressed as a percentage between 0 and 100%.

• Check throttle position sensor output signal

To check the output signal of the throttle position sensor, connect a multimeter between Pins B and C of the throttle position sensor connector. Set the meter to read "Duty Cycle." The duty cycle output of the throttle position sensor should be: - Low Idle: 16 ± 6% - High Idle: 85 ± 4%

• Throttle position sensor must be set with ET

NOTE: The throttle position sensor setting can be changed in the Engine ECM using the Configuration screen of ET. Two settings are available: 10% to 50% Throttle and 10% to 90% Throttle. The 777D Update truck must be set to the 10% to 90% Throttle setting.

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• Crankcase pressure sensor (arrow)

The crankcase pressure sensor (arrow) is located on the right side of the engine above the engine oil cooler. The crankcase pressure sensor provides an input signal to the Engine ECM. The ECM provides the signal to the Caterpillar Monitoring System, which informs the operator of the crankcase pressure. High crankcase pressure may be caused by worn piston rings or cylinder liners.

• Crankcase pressure event

If crankcase pressure exceeds 3.6 kPa (.5 psi) or 14.4 inches of water, a high crankcase pressure event will be logged. No factory password is required to clear this event.

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66

• EUI fuel injector solenoid (arrow)

Shown is the top of a cylinder head with the valve cover removed. The most important output from the Engine ECM is the Electronic Unit Injection (EUI) solenoid (arrow). One injector is located in each cylinder head. The engine control analyzes all the inputs and sends a signal to the injector solenoid to control engine timing and speed.

• Engine timing and speed

Engine timing is determined by controlling the start time that the injector solenoid is energized. Engine speed is determined by controlling the duration that the injector solenoid is energized.

• E-trim code number identifies injector performance range

3500B injectors are calibrated during manufacturing for precise injection timing and fuel discharge. After the calibration, a four-digit "E-trim" code number is etched on the injector tappet surface. The E-trim code identifies the injector's performance range.

• Trim code numbers are programmed into Engine ECM

When the injectors are installed into an engine, the trim code number of each injector is entered into the personality module (software) of the Engine ECM using the ECAP or ET service tool. The software uses the trim code to compensate for the manufacturing variations in the injectors and allows each injector to perform as a nominal injector.

• Enter new trim codes during injector service

When an injector is serviced, the new injector's trim code should be programmed into the Engine ECM. If the new trim code is not entered, the previous injector's characteristics is used. The engine will not be harmed if the new code is not entered, but the engine will not provide peak performance.

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3500B LOGGED EVENTS • AIR FILTER RESTRICTION

• HIGH AFTERCOOLER TEMPERATURE

• LOW OIL PRESSURE

• ENGINE OIL LEVEL LOW

• HIGH COOLANT TEMPERATURE • HIGH CRANKCASE PRESSURE • ENGINE OVERSPEED

• LOW COOLANT FLOW

• OIL FILTER RESTRICTION

• USER DEFINED SHUTDOWN

• FUEL FILTER RESTRICTION

• PRELUBE OVERRIDE

• HIGH EXHAUST TEMPERATURE

67 • Events logged by Engine ECM

The 3500B Engine ECM logs several data events that could cause damage to the engine. Some of the events require factory passwords to clear from the ECM memory. The events logged by the Engine ECM, their maximum derate and their trip points are listed below: Air filter restriction: Greater than 6.25 kPa (25 in. of water). Maximum derate of 20%. Factory password required.

• 40% derate with two sensor failures

If the atmospheric and turbo inlet pressure sensors both fail at the same time, a derate of 40% will occur. Low oil pressure: From less than 44 kPa (6.4 psi) at LOW IDLE to less than 250 kPa (36 psi) at HIGH IDLE. Factory password required. High coolant temperature: Greater than 107°C (226°F). Factory password required. Engine overspeed: Greater than 2200 rpm. Factory password required.

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• Additional logged events

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Oil filter restriction: Greater than 70 kPa (10 psi). No factory password required. Greater than 200 kPa (29 psi). Factory password required. Fuel filter restriction: Greater than 138 kPa (20 psi). No factory password required. Exhaust temperature high: Greater than 750°C (1382°F). Maximum derate of 20%. Factory password required. Aftercooler coolant temperature high: Greater than 107°C (226°F). Factory password required. Engine oil level low: No factory password required. Crankcase pressure high: Greater than 3.6 kPa (.5 psi) or 14.4 inches of water. No factory password required. Coolant flow low: Factory password required. User defined shutdown: The customer has the option of installing systems that will shut down the engine if desired. If the installed system sends a ground signal to the Engine ECM at connector J1 pin 19, a user defined shutdown will occur. Factory password required. The engine will only shutdown when ground speed is 0 and the parking brake is ENGAGED. Prelube override: Override the engine oil prelube system with the key start switch. Factory password required. (see Slide No. 69)

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SYSTEMS CONTROLLED BY ENGINE ECM • ETHER INJECTION • RADIATOR SHUTTER CONTROL • COOL ENGINE ELEVATED IDLE • COLD CYLINDER CUTOUT • ENGINE START FUNCTION • ENGINE OIL PRE-LUBRICATION

68 • Engine ECM controls other systems

The Engine ECM also regulates other systems by energizing solenoids or relays. Some of the other systems controlled by the ECM are:

• Ether injection

Ether Injection: The Engine ECM will automatically inject ether from the ether cylinders during cranking. The duration of automatic ether injection depends on the jacket water coolant temperature. The duration will vary from 10 to 130 seconds. The operator can also inject ether manually with the ether switch in the cab on the center console (see Slide No. 46). The manual ether injection duration is 5 seconds. Ether will be injected only if the engine coolant temperature is below 10¡C (50¡F) and engine speed is below 1900 rpm.

• Radiator shutter control

Radiator Shutter Control: On trucks that operate in cold weather, shutters can be added in front of the radiator. Installing shutters in front of the radiator allows the engine to warm up to operating temperature quicker. If a truck is equipped with the attachment radiator shutter control, the shutters are controlled by the Engine ECM.

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Cool Engine Elevated Idle: The Engine ECM provides an elevated engine idle speed of 1300 rpm when the engine coolant temperature is below 60°C (140°F). The rpm is gradually reduced to 1000 rpm between 60°C (140°F) and 71°C (160°F). When the temperature is greater than 71°C (160°F), the engine will operate at low idle (700 rpm). Increasing the low idle speed helps prevent incomplete combustion and overcooling. To temporarily reduce the elevated idle speed, the operator can release the parking brake or step on the throttle momentarily, and the idle speed will decrease to LOW IDLE for 10 minutes.

• Cold cylinder cutout

Cold Cylinder Cutout: The 3500B engine uses a cold cylinder cutout function to: - Reduce white exhaust smoke (unburned fuel) after start-up and during extended idling in cold weather - Minimize the time in Cold Mode - Reduce the use of ether injection. After the engine is started and the automatic ether injection system has stopped injecting ether, the Engine ECM will cut out one cylinder at a time to determine which cylinders are firing. The ECM will disable some of the cylinders that are not firing. The ECM can identify a cylinder which is not firing by monitoring the fuel rate and engine speed during a cylinder cutout. The ECM averages the fuel delivery and analyzes the fuel rate change during a cylinder cutout to determine if the cylinder is firing.

• Engine runs rough during Cold Mode

Disabling some of the cylinders during Cold Mode operation will cause the engine to run rough until the coolant temperature increases above the Cold Mode temperature. This condition is normal, but the operator should be aware it exists to prevent unnecessary complaints.

• Engine start function

Engine Start Function: The Engine Start function is controlled by the Engine ECM and the Transmission/Chassis ECM. The Engine ECM provides signals to the Transmission/Chassis ECM regarding the engine speed and the condition of the engine pre-lubrication system. The Transmission/Chassis ECM will energize the starter relay only when: - The shift lever is in NEUTRAL. - The parking brake is ENGAGED. - The engine speed is zero rpm. - The engine pre-lubrication cycle is completed or turned OFF. NOTE: To protect the starter, the starter is disengaged when the engine rpm is above 300 rpm.

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69 • Engine oil pre-lubrication 1. Pre-lubrication pump relay

2. Pre-lubrication pump

Engine Oil Pre-lubrication: Engine oil pre-lubrication is controlled by the Engine ECM and Transmission/Chassis ECM. The Engine ECM energizes the pre-lubrication pump relay located behind the cab (see Slide No. 53) The relay behind the cab then energizes the pre-lube relay (1) on the front engine mount. The Engine ECM signals the Transmission/Chassis ECM to crank the engine when: - Engine oil pressure is 3 kPa (.4 psi) or higher. - The pre-lubrication pump (2) has run for 17 seconds. (If the system times out after 17 seconds, a pre-lubrication time out fault is logged in the Engine ECM.) - The engine has been running in the last two minutes. - Coolant temperature is above 50°C (122°F).

• Pre-lubrication override

The engine oil pre-lubrication system can be bypassed to allow quick starts. To override the pre-lubrication system, turn the key start switch to the CRANK position for a minimum of two seconds. The Transmission/Chassis ECM will begin the pre-lube cycle. While the prelube cycle is active, turn the key start switch to the OFF position. Within 10 seconds, turn the key start switch back to the CRANK position. The Transmission/Chassis ECM will energize the starter relay.

• Pre-lubrication override event

If the engine oil pre-lubrication system is bypassed using the above procedure, the Engine ECM will log a pre-lube override event that requires a factory password to clear. NOTE: The ECAP and ET can enable or disable the pre-lubrication feature in the Engine ECM.

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Cooling Systems • Engine cooling systems: - Jacket water cooling system - Aftercooler cooling system

The cooling system is divided into two systems. The two systems are the jacket water cooling system and the aftercooler cooling system. When servicing the cooling systems, be sure to drain and fill both systems separately. The jacket water cooling system uses the cores on the right side of the radiator (approximately 60% of the total capacity). The jacket water cooling system temperature is controlled by temperature regulators (thermostats). The aftercooler cooling system uses the cores on the left side of the radiator (approximately 40% of the total capacity). The aftercooler cooling system does not have thermostats in the circuit. The coolant flows through the radiator at all times to keep the turbocharged inlet air cool for increased horsepower.

1. Coolant level gauges

The coolant levels are checked at the radiator top tank. Use the gauges (1) on the top tank to check the coolant level.

2. Pressure relief valves

Pressure relief valves (2) prevent the cooling systems from becoming over pressurized. The jacket water and the aftercooler cooling systems each have their own relief valve. If a cooling system overheats or if coolant is leaking from a relief valve, clean or replace the relief valve.

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Jacket Water Cooling System 1. Jacket water pump 2. Bypass tube 3. Jacket water thermostat housing

The jacket water pump (1) is located on the right side of the engine. The pump draws coolant from the bypass tube (2) until the temperature regulators (thermostats) open. The thermostats are located in the housing (3) at the top of the bypass tube. When the thermostats are open, coolant flows through the radiator to the water pump inlet.

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• Jacket water coolant temperature sensor (arrow)

The jacket water coolant temperature sensor (arrow) is located in the thermostat housing. The Engine ECM uses the coolant temperature sensor information for cold mode functions such as timing changes, elevated idle, cold cylinder cut-out, ether injection and others. The Engine ECM provides the signal to the Caterpillar Monitoring System, which informs the operator of the coolant temperature.

• High coolant temperature event

If the jacket water cooling system temperature increases above 107¡C (226¡F), the Engine ECM will log an event that requires a factory password to clear.

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1. Coolant flow warning switch

Coolant flows from the jacket water pump, past the coolant flow warning switch (1), and through the various system oil coolers (engine, hoist/converter/brake, and transmission). The coolant flow switch sends an input signal to the Engine ECM. The Engine ECM provides the input signal to the Caterpillar Monitoring System, which informs the operator of the coolant flow status.

• Low coolant flow event

If the ECM detects a low coolant flow condition, a low coolant flow event will be logged. A factory password is required to clear this event.

2. Jacket water coolant S•O•S tap

Jacket water coolant samples can be taken at the Scheduled Oil Sampling (S•O•S) coolant analysis tap (2).

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1. Engine oil cooler 2. Transmission oil cooler 3. Hoist, converter and brake oil cooler

Shown is the right side of the engine. Jacket water coolant flows through the engine oil cooler (1), the transmission oil cooler (2) and the hoist, converter and brake oil cooler (3) to both sides of the engine cylinder block. Coolant flows through the engine block and through the cylinder heads. From the cylinder heads, the coolant flows to the temperature regulators and either goes directly to the water pump through the bypass tube or to the radiator (depending on the temperature of the coolant).

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JACKET WATER COOLANT FLOW THERMOSTAT HOUSING

RADIATOR

ENGINE OIL COOLER BYPASS TUBE

TRANSMISSION OIL COOLER HOIST, CONVERTER AND BRAKE OIL COOLER

WATER PUMP

75 • Jacket water cooling circuit

Shown is the jacket water cooling circuit. Coolant flows from the jacket water pump through the coolers to the engine block. Coolant flows through the engine block and the cylinder heads. From the cylinder heads, the coolant flows to the temperature regulators (thermostats) and either goes directly to the water pump through the bypass tube or to the radiator (depending on the temperature of the coolant). In this illustration and those that follow, the colors used to identify the various pressures in the systems are: Red Green Red and White Stripes Brown Orange Blue Yellow Purple

- Supply oil/water pressure - Drain or tank oil/water - Reduced supply oil pressure - Lubrication or cooling pressure - Pilot or load sensing signal pressure - Blocked oil - Moving components - Air pressure

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Aftercooler Cooling System 1. Aftercooler water pump 2. Pump supply tube 3. Pump delivery tube 4. Aftercooler coolant S•O•S tap

The auxiliary (aftercooler) water pump (1) for the aftercooler cooling system is located on the left side of the engine. Coolant enters the aftercooler water pump from the radiator through the tube (2). Coolant flows from the pump to the aftercooler cores through the large tube (3) Aftercooler coolant samples can be taken at the Scheduled Oil Sampling (S¥O¥S) coolant analysis tap (4).

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1. Aftercooler 2. Aftercooler temperature sensor

• Aftercooler temperature event

Aftercooler coolant flows from the pump into the front of the aftercooler (1) and exits out the rear. Located in a tube at the rear of the aftercooler is the aftercooler temperature sensor (2). The aftercooler temperature sensor provides an input signal to the Engine ECM. The Engine ECM provides the input signal to the Caterpillar Monitoring System, which warns the operator if the aftercooler coolant temperature is too high. If the aftercooler coolant temperature increases above 107¡C (226¡F), the Engine ECM will log an event that requires a factory password to clear.

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1. Brake oil cooler • Aftercooler cooling circuit does not have thermostats

2. Brake oil cooler diverter valve

Coolant flows through the aftercooler core to the brake oil cooler (1) located at the rear of the engine. Coolant flows through the brake oil cooler to the aftercooler section of the radiator. The aftercooler cooling system does not have temperature regulators (thermostats) in the circuit. When the service or retarder brakes are ENGAGED, the brake oil cooler diverter valve (2) allows brake cooling oil to flow through the brake oil cooler. Normally, brake cooling oil is diverted around the cooler and goes directly to the brakes. Diverting oil around the cooler provides lower temperature aftercooler air during high power demands (when climbing a grade with the brakes RELEASED, for example).

3. Oil cooled front brake cooling oil ports

If the truck is equipped with the attachment front oil cooled brakes, the brake oil cooler tube will have two ports (3) for brake cooling oil to flow to the front brakes. If the truck is equipped with the standard front caliper disk brakes, the brake oil cooler tube will not have the two ports.

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AFTERCOOLER COOLANT FLOW RADIATOR BRAKE OIL COOLER

AFTERCOOLER

DIVERTER VALVE

AIR COMPRESSOR AFTERCOOLER WATER PUMP

79 • Aftercooler cooling circuit

Shown is the aftercooler cooling circuit. Coolant flows from the aftercooler water pump through the aftercooler and the air compressor. Coolant flows through the aftercooler core to the brake oil cooler located at the rear of the engine. Coolant then flows through the brake oil cooler to the aftercooler section of the radiator. The aftercooler cooling circuit does not have temperature regulators (thermostats) in the circuit.

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Lubrication System • Engine oil pump 1. Engine oil pump relief valve

The engine oil pump is located behind the jacket water pump on the right side of the engine. The pump draws oil from the oil pan through a screen. The relief valve (1) for the lubrication system is located on the pump. The engine also has a scavenge pump at the rear of the engine to transfer oil from the rear of the oil pan to the main sump.

2. Engine oil cooler bypass valve 3. Engine oil cooler

4. Engine oil level low switch

Oil flows from the pump through an engine oil cooler bypass valve (2) to the engine oil cooler (3). The bypass valve for the engine oil cooler permits oil flow to the system during cold starts when the oil is thick or if the cooler is plugged. An engine oil level switch (4) provides input signals to the Engine ECM. The Engine ECM provides an input signal to the Caterpillar Monitoring System, which warns the operator when the engine oil level is low and it is unsafe to operate the truck without causing damage to the engine. The ENGINE OIL LEVEL LOW message is a Category 2 or 3 Warning.

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• Engine oil filters

Oil flows from the engine oil cooler to the oil filters on the left side of the engine. The oil flows through the filters and enters the engine cylinder block to clean, cool and lubricate the internal components and the turbochargers.

1. Engine oil pressure sensor (filtered)

The engine has two oil pressure sensors. One sensor is located on each end of the oil filter base. The front sensor (see next slide) measures unfiltered oil pressure. The rear sensor (1) measures filtered oil pressure after the filters. The sensors send input signals to the Engine ECM. The ECM provides the input signal to the Caterpillar Monitoring System, which informs the operator of the engine oil pressure. Used together, the two engine oil pressure sensors inform the operator if the engine oil filters are restricted.

• Engine oil pressure event

If the engine oil pressure is less than 44 kPa (6.4 psi) at LOW IDLE to less than 250 kPa (36 psi) at HIGH IDLE, the Engine ECM will log an event that requires a factory password to clear.

• Engine oil filter restriction events

If the oil filter restriction exceeds 70 kPa (10 psi), a low oil filter restriction event will be logged. No factory password is required to clear this event. If the oil filter restriction exceeds 200 kPa (29 psi), a high oil filter restriction event will be logged. A factory password is required to clear this event.

2. Oil filter bypass valve covers

An oil filter bypass valve is located above each filter in the oil filter base behind the two covers (2). The oil filter bypass valves will open if the oil filter restriction exceeds 203 ± 20 kPa (29 ± 3 psi).

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1. Engine oil S•O•S tap

Shown is the bottom view of the engine oil filter base. Engine oil samples can be taken at the Scheduled Oil Sampling (S•O•S) tap (1) located on front of the oil filter base.

2. Engine oil pressure sensor (unfiltered)

Also shown is the engine oil pressure sensor (2) that measures the engine oil pressure before the filters.

3. Trapped engine oil drain

The oil filter base also has a fitting (3) that can be used to drain the engine oil trapped above the filters. Do not add oil through the fitting because unfiltered oil will enter the engine. Any contamination could cause damage to the engine.

NOTICE When changing the engine oil filters, drain the oil trapped above the filters through the fitting (3) to prevent spilling the oil. Oil added to the engine through the fitting will go directly to the main oil galleries without going through the engine oil filters. Adding oil to the engine through the fitting may introduce contaminants into the system and cause damage to the engine.

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ENGINE OIL SYSTEM ENGINE BLOCK

SCAVENGE PUMP ENGINE OIL FILTERS

BYPASS VALVE ENGINE OIL COOLER ENGINE OIL PUMP

83 • Engine oil system

The engine oil pump draws oil from the oil pan through a screen. The engine also has a scavenge pump at the rear of the engine to transfer oil from the rear of the oil pan to the main sump. Oil flows from the pump through an engine oil cooler bypass valve to the engine oil cooler. The bypass valve for the engine oil cooler permits oil flow to the system during cold starts when the oil is thick or if the cooler is plugged. Oil flows from the engine oil cooler to the oil filters. The oil flows through the filters and enters the engine cylinder block to clean, cool and lubricate the internal components and the turbochargers.

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84

Fuel System • Primary fuel filter (arrow)

The fuel tank is located on the right side of the truck (see Slide No. 13). Fuel is pulled from the tank through the primary fuel filter (arrow) by the fuel transfer pump located on the right side of the engine behind the engine oil pump.

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1. Fuel transfer pump 2. Fuel transfer pump bypass valve

The fuel transfer pump (1) is located behind the engine oil pump. The fuel transfer pump contains a bypass valve (2) to protect the fuel system components from excessive pressure. The bypass valve setting is higher [approximately 861 kPa (125 psi)] than the setting of the fuel pressure regulator (see Slide No. 87). Fuel flows from the transfer pump through the Engine ECM to the secondary fuel filters located on the left side of the engine.

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• Secondary fuel filters 1. Fuel priming pump

The secondary fuel filters and the fuel priming pump (1) are located above the engine oil filters on the left side of the engine. The fuel priming pump is used to fill the filters after they are changed.

2. Fuel filter bypass switch

Fuel filter restriction is monitored with a fuel filter bypass switch (2) located on the fuel filter base. The fuel filter bypass switch provides an input signal to the Engine ECM. The ECM provides a signal to the Caterpillar Monitoring System, which informs the operator if the secondary fuel filters are restricted.

• Fuel filter restriction event

If fuel filter restriction exceeds 138 kPa (20 psi), a fuel filter restriction event is logged. No factory password is required to clear this event.

• Fuel flows to EUI injectors

Fuel flows from the fuel filter base through the Electronic Unit Injection (EUI) fuel injectors (see Slide No. 66), the fuel pressure regulator and then returns to the fuel tank. The injectors receive 4 1/2 times the amount of fuel needed for injection. The extra fuel is used for cooling.

• Extra fuel cools injectors

NOTE: If the fuel system requires priming, it may be necessary to block the fuel return line during priming to force the fuel into the injectors.

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1. Fuel pressure tubes to injectors 2. Fuel pressure regulator

Fuel flows from the fuel filter base through the steel tubes (1) to the EUI fuel injectors. Return fuel from the injectors flows through the fuel pressure regulator (2) before returning to the fuel tank. Fuel pressure is controlled by the fuel pressure regulator. Fuel pressure should be between 360 to 725 kPa (52 to 105 psi) at Full Load RPM.

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FUEL SYSTEM FUEL TANK

FUEL PRESSURE REGULATOR

PRIMARY FUEL FILTER

CYLINDER HEAD

FUEL TRANSFER PUMP FUEL PRIMING PUMP

SECONDARY FUEL FILTERS

ENGINE ECM

CYLINDER HEAD

88 • Fuel system circuit

Fuel is pulled from the tank through the primary fuel filter by the fuel transfer pump. Fuel flows from the transfer pump through the Engine ECM to the secondary fuel filters. Fuel flows from the fuel filter base through the fuel injectors in the cylinder heads. Return fuel from the injectors flows through the fuel pressure regulator before returning to the tank. The fuel priming pump is used to fill the filters after they are changed. If the fuel system requires priming, it may be necessary to block the fuel return line during priming to force the fuel into the injectors.

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89 Air Induction and Exhaust System • Engine air intake system components: 1. Air filter restriction indicators • Alert indicator on dash

Shown are the air intake system components. Check the air filter restriction indicators (1). If the yellow pistons are in the red zone (indicating that the filters are plugged), the air filters must be serviced. An air filter restriction indicator is also located on the dash (see Slide No. 47). The alert indicator lights when the filter restriction is approximately 6.2 kPa (25 in. of water).

2. Dust valves

Located next to the air filter housings are the precleaners. Check the dust valves (2) for plugging. If necessary, disconnect the clamp and open the cover for additional cleaning. Replace the dust valve if the rubber is not flexible.

• Replace dust valve if not flexible

The dust valve is OPEN when the engine is OFF and closes when the engine is running. The dust valve must be flexible and close when the engine is running or the precleaner will not function properly and the air filters will have a shortened life.

• Large primary element

Two filter elements are installed in the filter housings. The large element is the primary element and the small element is the secondary element.

• Small secondary element

Air intake system tips: - The primary element can be cleaned a maximum of six times. - Never clean the secondary element for reuse. Always replace the secondary element. - Air filter restriction causes black exhaust smoke and low power.

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90

• Turbocharger inlet pressure sensor (arrow)

The turbocharger inlet pressure sensor (arrow) is located in a tube between the air filters and the turbochargers. The Engine ECM uses the turbocharger inlet pressure sensor in combination with the atmospheric pressure sensor to determine air filter restriction. The ECM provides the input signal to the Caterpillar Monitoring System, which informs the operator of the air filter restriction.

• Air filter restriction event

If air filter restriction exceeds 6.25 kPa (25 in. of water), an air filter restriction event will be logged, and the ECM will derate the fuel delivery (maximum derating of 20%) to prevent excessive exhaust temperatures. A factory password is required to clear this event. If the Engine ECM detects a turbocharger inlet pressure sensor fault, the ECM will derate the engine to the maximum rate of 20%. If the Engine ECM detects a turbocharger inlet and atmospheric pressure sensor fault at the same time, the ECM will derate the engine to the maximum rate of 40%.

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• 3508B has two turbochargers 1. Turbo turbine

2. Aftercooler

The 3508B engine is equipped with two turbochargers. The turbochargers are driven by the exhaust gas from the cylinders which enters the turbine side (1) of the turbochargers. The exhaust gas flows through the turbochargers, the exhaust piping, and the mufflers. The clean air from the filters enters the compressor side of the turbochargers. The compressed air from the turbochargers flows to the aftercooler (2). After the air is cooled by the aftercooler, the air flows to the cylinders and combines with the fuel for combustion.

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• Exhaust temperature sensor (arrow)

An exhaust temperature sensor (arrow) is located in each exhaust manifold before the turbochargers. The two exhaust temperature sensors provide input signals to the Engine ECM. The ECM provides the input signal to the Caterpillar Monitoring System, which informs the operator of the exhaust temperature.

• Causes of high exhaust temperature

Some causes of high exhaust temperature may be faulty injectors, plugged air filters, or a restriction in the turbochargers or the muffler.

• High exhaust temperature derates engine and logs event

If the exhaust temperature is above 750¡C (1382¡F), the Engine ECM will derate the fuel delivery to prevent excessive exhaust temperatures. The ECM will derate the engine by 2% for each 30 second interval that the exhaust temperature is above 750¡C (1382¡F) (maximum derate of 20%). The ECM will also log an event that requires a factory password to clear.

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93

• Turbo outlet pressure sensor (arrow)

Shown is the turbocharger outlet pressure sensor (arrow). The turbocharger outlet pressure sensor sends an input signal to the Engine ECM. The Engine ECM compares the value of the turbo outlet pressure sensor with the value of the atmospheric pressure sensor and calculates boost pressure.

• Check for power problem

The best way to check for a power problem is to compare the truck performance with the rimpull charts in the performance handbook (SEBD0340) or the 777D Update Specalog. The truck should be able to climb a grade in the same gear as specified in these two publications.

• Determine which power train component has problem

If an engine power problem is suspected, check boost pressure at full load rpm. If boost pressure is correct at full load rpm, the engine is not the problem and other systems such as the torque converter should be checked.

• Check boost at full load rpm

To check boost pressure at full load rpm, the truck must be operated in FIRST GEAR with the throttle at MAXIMUM and the retarder gradually engaged. Traveling up a grade is best as long as the engine rpm does not fall below the full load rpm specification during the test. Gradually engage the retarder until the full load rpm is displayed. When the full load rpm is displayed, record the boost pressure. If boost pressure is within the specifications at full load rpm, the engine is operating correctly.

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Use ET or the Caterpillar Monitoring System display panel to view the engine rpm and boost pressure. The boost and full load rpm specifications are: • Full load boost pressure

Engine ECM set to 746 kW (1000 hp) - Boost: 221 ± 28 kPa (32 ± 4 psi) - Full load: 1750 rpm Engine ECM set to 686 kW (920 hp) - Boost: 201 ± 28 kPa (29 ± 4 psi) - Full load: 1750 rpm

• Torque converter stall speed

Generally, Torque Converter (TC) stall speed (in gear, full throttle, zero ground speed) is used to determine if the engine power is low or a torque converter problem exists. For example, if the engine power is within specification and the stall speed is high, the torque converter may have a problem (low internal oil pressure, poor internal tolerances or damaged components). The boost and torque converter stall rpm specifications are:

• Torque converter stall boost pressure

Engine ECM set to 746 kW (1000 hp) - Boost: 210 ± 28 kPa (30 ± 4 psi) - Torque Converter Stall: 1540 to 1670 rpm Engine ECM set to 686 kW (920 hp) - Boost: 190 ± 28 kPa (28 ± 4 psi) - Torque Converter Stall: 1540 to 1670 rpm

NOTE: On the 777D Update truck, the horsepower can be changed from 686 kW (920 hp) to 746 kW (1000 hp) by programming the Engine ECM with the ET Service Tool.

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FROM AIR FILTERS

AIR INDUCTION AND EXHAUST SYSTEM

MUFFLER

AFTERCOOLER

FROM AIR FILTERS

94 • Air induction and exhaust system

This schematic shows the flow through the air induction and exhaust system. The turbochargers are driven by the exhaust gas from the cylinders which enters the turbine side of the turbochargers. The exhaust gas flows through the turbochargers, the exhaust piping, and the mufflers. The clean air from the filters enters the compressor side of the turbochargers. The compressed air from the turbochargers flows to the aftercooler. After the air is cooled by the aftercooler, the air flows to the cylinders and combines with the fuel for combustion.

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POWER TRAIN 777D

95 POWER TRAIN • Power train components: - Torque converter - Transfer gears - Transmission - Differential - Final drives

Power flows from the engine to the rear wheels through the power train. The components of the power train are: -

Torque converter Transfer gears Transmission Differential Final drives

INSTRUCTOR NOTE: In this section of the presentation, component locations and a brief description of the component functions are provided. For more detailed information on the torque converter and ICM (Individual Clutch Modulation) transmission, refer to the Technical Instruction Module "769C - 793B Off-highway Trucks-Torque Converter and Transmission Hydraulic System" (Form SEGV2591).

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3

1

2 4 5

96

Torque Converter • Torque converter: - Provides a fluid coupling - Multiplies torque - Provides direct drive operation

1. Inlet relief valve

The first component in the power train is the torque converter. The torque converter provides a fluid coupling that permits the engine to continue running with the truck stopped. In converter drive, the torque converter multiplies engine torque to the transmission. At higher ground speeds, a lockup clutch engages to provide direct drive. The NEUTRAL and REVERSE ranges are converter drive only. FIRST SPEED is converter drive at low ground speed and direct drive at high ground speed. SECOND through SEVENTH SPEEDS are direct drive only. The torque converter goes to converter drive between each shift (during clutch engagement) to provide smooth shifts. Mounted on the torque converter are the inlet relief valve (1), the outlet relief valve (2) and the torque converter lockup clutch control valve (3).

2. Outlet relief valve 3. Lockup clutch control valve 4. Outlet temperature sensor 5. Torque converter pump

A torque converter outlet temperature sensor (4) provides an input signal to the Transmission/Chassis ECM. The Transmission/Chassis ECM sends the signal to the Caterpillar Monitoring System, which informs the operator of the torque converter outlet temperature. The torque converter pump (5) consists of three or four sections. The pump sections from front to rear are: - torque converter scavenge - torque converter charging - parking brake release - brake cooling (oil cooled front brakes only)

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LOCKUP PISTON

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TURBINE

IMPELLER

TORQUE CONVERTER CONVERTER DRIVE STATOR

FREEWHEEL ASSEMBLY

TORQUE CONVERTER INLET OIL

TORQUE CONVERTER LOCKUP OIL PASSAGE

97 • CONVERTER DRIVE - Output shaft rotates slower than engine rpm - Torque is increased • Torque converter components: - Lockup clutch - Impeller - Turbine - Stator

This sectional view shows a torque converter in CONVERTER DRIVE. The lockup clutch (yellow piston and blue discs) is not engaged. During operation, the rotating housing and impeller (red) can rotate faster than the turbine (blue). The stator (green) remains stationary and multiplies the torque transfer between the impeller and the turbine. The output shaft rotates slower than the engine crankshaft, but with increased torque.

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LOCKUP PISTON

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TURBINE

IMPELLER

TORQUE CONVERTER DIRECT DRIVE STATOR

TORQUE CONVERTER INLET OIL

FREEWHEEL ASSEMBLY

TORQUE CONVERTER LOCKUP OIL PASSAGE

98 • DIRECT DRIVE - Lockup clutch engaged - Output shaft rotates at engine rpm - Stator freewheels

In DIRECT DRIVE, the lockup clutch is engaged by hydraulic pressure and locks the turbine to the impeller. The housing, impeller, turbine, and output shaft then rotate as a unit at engine rpm. The stator, which is mounted on a freewheel assembly, is driven by the force of the oil in the housing and will freewheel at approximately the same rpm.

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3

4

1 2 5

99

Torque Converter Hydraulic System • Torque converter pump has three or four sections: 1. Torque converter scavenge 2. Torque converter charging 3. Parking brake release 4. Brake oil cooling (oil cooled front brakes only) 5. Torque converter scavenge screen cover

The three (caliper disc front brakes) or four (oil cooled front brakes) section torque converter pump is located at the bottom rear of the torque converter. The four sections (from the front to the rear) are: -

Torque converter scavenge (1) Torque converter charging (2) Parking brake release (3) Brake oil cooling (4) (oil cooled front brakes only)

Excess oil that accumulates in the bottom of the torque converter is scavenged by the first section of the pump through a screen behind the access cover (5) and returned to the hydraulic tank.

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1

2

100

1. Torque converter charging filter

Oil flows from the torque converter charging section of the pump to the torque converter charging filter (1). The filter is located on the frame behind the left front tire.

2. Hoist, converter and brake oil S•O•S tap

Hoist, converter and brake oil samples can be taken at the Scheduled Oil Sampling (S¥O¥S) tap (2).

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1 2

3 4

5

101

1. Torque converter inlet relief valve 2. Inlet relief pressure test port

Oil flows from the torque converter charging filter to the torque converter inlet relief valve (1). The inlet relief valve limits the maximum pressure of the supply oil to the torque converter. The torque converter inlet relief pressure can be measured at this valve by removing a plug (2) and installing a pressure tap. Inlet relief pressure should not exceed 930 ± 35 kPa (135 ± 5 psi) at high idle when the oil is cold. Normally, the inlet relief pressure will be slightly higher than the outlet relief valve pressure. Oil flows through the inlet relief valve and enters the torque converter.

3. Torque converter outlet relief valve 4. Torque converter outlet relief pressure tap

5. Torque converter outlet temperature sensor

Some of the oil will leak through the torque converter to the bottom of the housing to be scavenged. Most of the oil in the torque converter is used to provide a fluid coupling and flows through the torque converter outlet relief valve (3). The outlet relief valve maintains the minimum pressure inside the torque converter. The main function of the outlet relief valve is to keep the torque converter full of oil to prevent cavitation. The outlet relief pressure can be measured at the tap (4) on the outlet relief valve. The outlet relief pressure should be 380 to 515 kPa (55 to 75 psi) at 1540 to 1670 rpm (TC Stall). A torque converter outlet temperature sensor (5) provides an input signal to the Caterpillar Monitoring System, which informs the operator of the torque converter outlet temperature.

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1 2

102

2. Hoist, converter and brake oil cooler

Most of the oil from the torque converter outlet relief valve flows through a screen (1) and the hoist, converter and brake oil cooler (2) located on the right side of the engine.

• TC charging oil cools rear brakes

The torque converter charging oil flows through the hoist, converter and brake oil cooler and the rear brakes before returning to the hydraulic tank.

1. Cooler screen

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103

• Parking brake release filter (arrow)

Oil flows from the parking brake release section of the torque converter pump to the parking brake release filter (arrow).

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1

2

104

1. Parking brake release valve

Oil from the parking brake release filter flows to the parking brake release valve (1). The valve is located inside the left frame near the torque converter. The parking brake release section of the torque converter pump provides supply oil for several purposes: -

Release the parking brakes Engage the torque converter lockup clutch Hoist valve pilot oil Brake oil cooling

2. Parking brake relief valve

The parking brake relief valve (2) controls the pressure for parking brake release, torque converter lockup and hoist valve pilot oil. The parking brake release pressure is 4700 ± 200 kPa (680 ± 30 psi).

• Most oil used for brake cooling

Most of the oil from the parking brake release valve flows through the brake oil cooler and is used to cool the brakes.

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2

1 3

105

1. Torque converter lockup clutch valve supply port 2. Lockup solenoid

The parking brake release pump supplies oil to the torque converter lockup clutch valve through the inlet port (1). When the lockup clutch solenoid (2) is energized by the Transmission/Chassis ECM, parking brake release oil is used to start the modulation process for torque converter lockup. The lockup clutch valve then supplies oil to ENGAGE the lockup clutch in the torque converter.

3. Torque converter lockup clutch pressure tap

Torque converter lockup clutch pressure can be tested at the tap (3). With engine speed at1300 rpm, torque converter lockup clutch pressure should be 2135 ± 70 kPa (310 ± 10 psi).

• Lockup clutch pressure test

To check the lockup clutch pressure, the transmission must be in NEUTRAL. Disconnect the connectors from the upshift and downshift solenoids. The downshift solenoid is always energized in NEUTRAL. Therefore, +24 Volts will be available at the downshift solenoid harness connector to energize the lockup solenoid. With the engine rpm at LOW IDLE, use two jumper wires to connect the downshift solenoid harness to the lockup solenoid. The lockup clutch will engage.

• Lockup clutch pressure adjustment

The lockup clutch maximum pressure is not adjustable. If the lockup clutch maximum pressure is not correct, verify that the lockup clutch primary pressure is correct. If the lockup clutch primary pressure is correct, check for loose or sticking components or debris in the valve. If these components are not the problem, change the load piston springs. If the load piston springs are replaced, be sure to reset the lockup clutch primary pressure.

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LOCKUP CLUTCH VALVE TORQUE CONVERTER DRIVE LOAD PISTON

MODULATION REDUCTION VALVE

SELECTOR PISTON

LOAD PISTON ORIFICE PRESSURE REDUCTION VALVE

LOCKUP SOLENOID

SHUTTLE VALVE

TO LOCKUP CLUTCH

FROM PARKING BRAKE PUMP

106 • Lockup clutch valve in TC drive

• Supply pressure is reduced to pilot pressure

Shown is a sectional view of the torque converter lockup clutch valve in TORQUE CONVERTER DRIVE or NEUTRAL. Supply oil from the parking brake release pump is used to provide lockup clutch oil and has two functions: 1. Supply pressure is reduced to provide pilot pressure to the solenoid valve. 2. When the solenoid is energized, supply pressure is reduced by the modulation reduction valve to provide lockup clutch pressure. First, supply pressure is reduced to provide pilot pressure to the lockup solenoid. Supply oil to the pressure reduction valve flows through crossdrilled orifices in the spool, past a check valve and enters the slug chamber. The check valve dampens spool movement and reduces the possibility of valve chatter and pressure fluctuation. Oil pressure moves the slug in the right end of the spool to the right and the spool moves to the left against the spring force. The slug reduces the effective area on which the oil pressure can push. Because of the reduced effective area, a smaller, more sensitive spring can be used. Pilot pressure will be equal to the force of the spring on the left end of the spool. The spring force can be adjusted with shims. Pilot pressure is 1725 ± 70 kPa (250 ± 10 psi).

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LOCKUP CLUTCH VALVE DIRECT DRIVE

LOAD PISTON

MODULATION REDUCTION VALVE

SELECTOR PISTON

LOAD PISTON ORIFICE PRESSURE REDUCTION VALVE

LOCKUP SOLENOID

ON

SHUTTLE VALVE

TO LOCKUP CLUTCH

FROM POWER TRAIN PUMP

107 • Lockup clutch valve in DIRECT DRIVE

Shown is a sectional view of the torque converter lockup clutch valve in DIRECT DRIVE.

• Energized lockup solenoid starts clutch modulation

When the lockup solenoid is energized, pilot oil moves a shuttle valve to the right, which closes the lower left drain passage and opens the check valve. Oil then flows to the selector piston. Moving the selector piston blocks the upper drain passage, and the load piston springs are partially compressed.

• Lockup clutch at primary pressure

When the load piston that compresses the springs is at the top against the selector piston, lockup clutch pressure is at its lowest controlled value. This value is called "primary pressure." Primary pressure is 1030 ± 35 kPa (150 ± 5 psi).

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• Lockup clutch at maximum pressure

As the load piston moves down, the lockup clutch pressure increases gradually until the load piston stops. The final lockup clutch pressure is then reached. The final (maximum) lockup clutch pressure should be 2135 ± 70 kPa (310 ± 10 psi). The gradual increase in pressure, which depends on how fast the load piston moves, is called "modulation."

• Load piston orifice determines modulation time

The speed of the load piston movement depends on how fast the oil can flow to the area above the load piston. The load piston orifice meters the flow of oil to the load piston chamber and determines the modulation time.

• Primary pressure adjusted with shims

The primary pressure is adjusted with shims in the load piston. The final lockup clutch pressure is not adjustable. If the primary pressure is correct and the final lockup clutch pressure is incorrect, the load piston should be checked to make sure that it moves freely in the selector piston. If the load piston moves freely, the load piston springs should be replaced.

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TORQUE CONVERTER HYDRAULIC SYSTEM CALIPER DISC FRONT BRAKES REAR BRAKES DIVERTER VALVE

HOIST VALVE

BRAKE OIL COOLER (BEHIND ENGINE)

TO BRAKE MAKEUP TANK TORQUE CONVERTER CHARGING FILTER

INLET RELIEF VALVE OUTLET RELIEF VALVE

PARKING BRAKE RELEASE VALVE

CONVERTER LOCKUP VALVE

TO TCS VALVE PARKING BRAKE FILTER HOIST, CONVERTER AND BRAKE OIL COOLER

TO TCS VALVE TO TOW VALVE AND HOIST PILOT

SCREEN CONVERTER SCAVENGE SCREEN

108 • Converter hydraulic system with caliper disc front brakes

This schematic shows the flow of oil from the torque converter pump through the torque converter hydraulic system on the 777D Update truck with caliper disc front brakes.

• Scavenge pump section

The scavenge pump section pulls oil through a screen from the torque converter housing and sends the oil to the hydraulic tank.

• Charging pump section

The charging pump section sends oil through the torque converter charging filter to the torque converter inlet relief valve. Oil flows from the inlet relief valve through the torque converter to the outlet relief valve. Oil flows from the outlet relief valve through the torque converter oil cooler to the rear brakes.

• Parking brake release pump section

The parking brake release pump section sends oil through the parking brake release filter to the parking brake release valve and the torque converter lockup clutch valve. Most of the oil flows through the parking brake release valve and the torque converter oil cooler to the rear brakes.

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FRONT BRAKES

TORQUE CONVERTER HYDRAULIC SYSTEM REAR BRAKES

OIL COOLED FRONT BRAKES RIGHT

DIVERTER VALVE

HOIST VALVE

LEFT

BRKAE OIL COOLER (BEHIND ENGINE)

TORQUE CONVERTER CHARGING FILTER

TO BRAKE MAKEUP TANK INLET RELIEF VALVE OUTLET RELIEF VALVE

PARKING BRAKE RELEASE VALVE

CONVERTER LOCKUP VALVE

TO TCS VALVE

TO TCS VALVE

PARKING BRAKE FILTER

TO TOW VALVE AND HOIST PILOT

HOIST, CONVERTER AND BRAKE OIL COOLER

109 • Converter hydraulic system with oil cooled front brakes

This schematic shows the flow of oil from the torque converter pump through the torque converter hydraulic system on the 777D Update truck with oil cooled front brakes.

• Scavenge pump section

The scavenge pump section pulls oil through a screen from the torque converter housing and sends the oil to the hydraulic tank.

• Charging pump section

The charging pump section sends oil through the torque converter charging filter to the torque converter inlet relief valve. Oil flows from the inlet relief valve through the torque converter to the outlet relief valve. Oil flows from the outlet relief valve through the torque converter oil cooler to the rear brakes.

• Parking brake release pump section

The parking brake release pump section sends oil through the parking brake release filter to the parking brake release valve and the torque converter lockup clutch valve. Most of the oil flows through the parking brake release valve and the brake oil cooler to the front and rear brakes.

• Brake cooling pump section

The brake cooling pump section of the torque converter pump (oil cooled front brakes only) sends additional oil through the torque converter oil cooler located on the right side of the engine to the rear brakes.

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2 3 1

110

Transmission and Transfer Gears 1. Transfer gears 2. Transmission

Power flows from the torque converter through a drive shaft to the transfer gears (1). The transfer gears are splined to the transmission input shaft.

3. Differential

The transmission (2) is located between the transfer gears and the differential (3). The transmission is electronically controlled and hydraulically operated as in all other ICM (Individual Clutch Modulation) transmissions in Caterpillar rigid frame trucks.

• Transmission is power shift planetary design

The transmission is a power shift planetary design which contains seven hydraulically engaged clutches. The transmission provides seven FORWARD speeds and one REVERSE speed. The differential is located in the rear axle housing behind the transmission. Power from the transmission flows through the differential and is divided equally to the final drives in the rear wheels. The final drives are single reduction planetaries.

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2

3 1

111

Transmission Hydraulic System • Transmission two section pump: 1. Transmission scavenge 2. Transmission charging 3. Magnetic scavenge screen cover

The two section transmission pump is mounted on the rear of the pump drive, which is located inside the right frame near the torque converter. The two sections are: - Transmission scavenge (1) - Transmission charging (2) The transmission scavenge section pulls oil from the bottom of the transmission case through the magnetic screen located below the cover (3). The magnetic screen should always be checked for debris if a problem with the transmission is suspected. The scavenged oil from the transmission flows through the transmission oil cooler (see Slide No. 74) and returns to the transmission tank. The transmission charging section pulls oil from the transmission tank. Charging oil flows from the pump through a transmission charging filter to the hydraulic controls in the transmission.

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2 3

1

112 1. Transmission charging filter

Oil flows from the charging section of the transmission pump to the transmission charging filter (1) located on the frame behind the right front tire. Oil flows from the transmission charging filter to the transmission control valve located on top of the transmission.

2. Transmission S•O•S tap

Transmission oil samples can be taken at the Scheduled Oil Sampling (S•O•S) tap (2).

3. Oil filter bypass switch

An oil filter bypass switch (3) is located on the filter. The oil filter bypass switch provides an input signal to the Caterpillar Monitoring System, which informs the operator if the filter is restricted.

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4

3

5

2

1

113

1. Transmission control valve supply port

The transmission charging pump supplies oil to the transmission hydraulic control valve and the shift solenoids through the inlet port (1). Excess transmission charging oil drops to the bottom of the housing to be scavenged.

2. Priority valve pilot pressure plug

The transmission hydraulic control valve contains a priority valve. The priority valve controls the pilot pressure that is directed to the selector pistons in each of the clutch stations. The pilot pressure is 1720 kPa (250 psi) and can be measured at the plug (2).

3. Transmission charging pressure tap

The transmission charging pressure relief valve is part of the transmission hydraulic control valve. The relief valve limits the maximum pressure in the transmission charging circuit. Transmission charging pressure can be measured at the tap (3). At LOW IDLE in TORQUE CONVERTER DRIVE, transmission charging pressure should be 2480 kPa (360 psi) minimum. At HIGH IDLE in TORQUE CONVERTER DRIVE, transmission charging pressure should be 3200 kPa (465 psi) maximum.

4. Transmission clutch pressure taps

Shown is the Individual Clutch Modulation (ICM) transmission hydraulic control valve. Transmission clutch pressures are measured at the pressure taps (4).

5. Transmission lube relief valve

The transmission lube pressure relief valve (5) limits the maximum pressure in the transmission lube circuit. The lubrication oil is used to cool and lubricate all of the gears, bearings and clutches in the transmission and transfer gears.

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114

• Transmission lube oil pressure tap (arrow)

The transmission lube pressure relief valve is in the transmission case on the transmission hydraulic control valve (see previous slide). The relief valve limits the maximum pressure in the transmission lube circuit. Transmission lube oil pressure can be measured at the tap (arrow) on top of the transfer gear case. At LOW IDLE, the transmission lube pressure should be 3 to 41 kPa (.5 to 6 psi). At HIGH IDLE, the transmission lube pressure should be 83 to 138 kPa (12 to 20 psi).

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TRANSMISSION HYDRAULIC SYSTEM NEUTRAL DOWNSHIFT PRESSURE

UPSHIFT PRESSURE

A DOWNSHIFT SOLENOID

UPSHIFT SOLENOID ROTARY ACTUATOR

CHARGING FILTER PUMP PRESSURE

E

ON

B NEUTRALIZER VALVE

PILOT OIL PRESSURE

PRIORITY REDUCTION VALVE

F

ROTARY SELECTOR SPOOL

C

OIL COOLER CHARGING PUMP

SCAVENGE PUMP

G

D

RELIEF VALVE

H

TRANSMISSION CASE

TANK

LUBE RELIEF VALVE

SELECTOR VALVE GROUP

PRESSURE CONTROL GROUP

LUBE PRESSURE

115 • Transmission in NEUTRAL • Priority reduction valve

• Neutralizer valve

This schematic shows the conditions in the system with the ENGINE STARTED and the transmission in NEUTRAL. The priority reduction valve is installed in the bore on the left side of the valve body. This valve has two functions: It controls the pressure of the pilot oil (orange) that is used to initiate clutch engagement, and it makes sure that pilot pressure is available at the neutralizer valve before pressure oil (red) is sent to the remainder of the system. The neutralizer valve moves only when the rotary selector spool is in the NEUTRAL position. When the rotary selector spool is in the NEUTRAL position and the engine is started, pump oil flows through a passage in the center of the neutralizer valve, flows up around the check ball, pressurizes the top of the valve, and then moves down. In this position, the neutralizer valve directs pilot oil to the center of the rotary selector spool. If the rotary selector spool is not in the NEUTRAL position during engine start-up, the neutralizer valve will block the flow of pilot oil to the rotary selector spool.

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• Main relief valve • Lube relief valve

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Directly below the neutralizer valve is the main relief valve. This valve limits the maximum system pressure during operation. Excess pump oil is directed to the lubrication circuit and the pressure is maintained by the lube relief valve. The lubrication oil is used to cool and lubricate all of the gears, bearings and clutches in the transmission and transfer gears. To initiate a shift, pressure oil from either the upshift or downshift solenoid is sent to the rotary actuator. Inside the actuator housing is a rotating vane which divides the actuator into two chambers. Pressure oil from the upshift solenoid causes the vane to rotate in one direction while pressure oil from the downshift solenoid causes the vane to rotate in the opposite direction. The vane is connected to and causes rotation of the rotary selector spool inside the selector valve group.

• Downshift solenoid ON in NEUTRAL

The transmission hydraulic system is equipped with a two section gear pump. From the charging section of the pump, the oil flows through the filter and is sent directly to the two solenoids and the selector valve group. Pump flow is blocked at the upshift solenoid and, because the downshift solenoid is continuously energized in NEUTRAL, the valve in the solenoid is open. This condition permits oil to flow to the rotary actuator. Pressure on the downshift side of the rotating vane in the rotary actuator keeps the vane and the rotary selector spool in the NEUTRAL position until a shift is made.

• Rotary selector spool

The rotary selector spool is actually a hollow rotating shaft. A plug and screen assembly inside the spool divides the center cavity into two separate oil chambers.

- Contains plug and screen assembly - Selects clutch combinations

During operation, pilot oil from the upper chamber is directed to the pressure control valve group to initiate clutch engagement. For any gear except NEUTRAL, two of the outlet ports from the upper chamber are aligned with drilled passages in the selector valve body. For NEUTRAL, only one outlet port permits pilot oil to flow to the pressure control valve group. The lower chamber in the rotary selector spool is always open to drain. For each gear position except NEUTRAL, all but two of the drain ports are open to drain. Whenever a clutch station is engaged, the lower half of the spool blocks the drain passage to that station.

• Excess case oil returned to tank

All oil that is in the bottom of the transmission case is returned to the tank by the transmission scavenge section of the transmission pump.

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TRANSMISSION HYDRAULIC SYSTEM FOURTH SPEED FORWARD

DOWNSHIFT PRESSURE DOWNSHIFT SOLENOID

UPSHIFT PRESSURE

A

UPSHIFT SOLENOID ROTARY ACTUATOR

CHARGING FILTER

E

PUMP PRESSURE

B 4 NEUTRALIZER VALVE PRIORITY REDUCTION VALVE

PILOT OIL PRESSURE

N

F

ROTARY SELECTOR SPOOL

C

OIL COOLER CHARGING PUMP

SCAVENGE PUMP

G

D

RELIEF VALVE

H

TRANSMISSION CASE

TANK

LUBE RELIEF VALVE

SELECTOR VALVE GROUP

PRESSURE CONTROL GROUP

LUBE PRESSURE

116 • Fourth speed FORWARD

This schematic shows the components and the oil flow in the system during operation in FOURTH GEAR. The upshift solenoid is energized and directs pump oil to the rotary actuator. The rotary actuator moves the rotary selector spool to the FOURTH SPEED FORWARD position and the upshift solenoid is de-energized. The rotary spool selects two stations (C and E) which modulate the two clutches.

• Upshifts - clockwise direction

To shift from NEUTRAL to any other gear, the rotating vane must turn in the clockwise direction to the selected gear position. When the shift is indicated, pressure oil from the upshift solenoid is sent to the lower inlet port. The pressure oil moves the check valve toward the center of the actuator housing until the check valve covers a drain passage located near the inner end of the inlet passage. The pressure oil then flows through the check valve and fills the small space between the two vanes.

• Opens check valve, closes drain passage

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As the pressure increases, the rotating vane moves in the clockwise direction to the appropriate gear position. Any oil that was in the chamber on the nonpressurized (downshift) side of the vane is forced out of the chamber by the movement of the vane. • Closes check valve, opens drain passage

As the oil flows out of the chamber, it moves the upper check valve away from the center of the actuator housing. This movement opens a drain passage located near the inner end of the upper check valve passage and permits the oil to flow out of the center chamber. The check valve closes and prevents oil from flowing to the other solenoid.

• Downshifts counterclockwise direction

This sequence is just the opposite for downshifts (when the rotating vane moves in the counterclockwise direction).

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VALVE STATION SLUG

BALL CHECK VALVE

CLUTCH RELEASED LOAD PISTON

SELECTOR PISTON

PILOT OIL PASSAGE

PLUG

DECAY ORIFICE MODULATION REDUCTION VALVE

DRAIN

FROM PUMP

TO CLUTCH

LOAD PISTON ORIFICE

LOAD PISTON PLUG

CLUTCH PRESSURE TAP

117 • All stations contain same basic components

Since all seven valve stations contain the same basic components, an explanation of the operation of one station can be applied to the operation of the remaining six stations (including the lockup clutch station).

• Load piston orifices control modulation

The seven stations that control the clutches contain load piston orifices (sometimes called "cascade" orifices). The load piston orifices control the clutch modulation. The thicker the orifice, the faster the modulation. The retaining springs for the load piston orifices are identical, but the orifices vary in thickness from one station to another. Many of the stations are equipped with decay orifices. Check the parts book for proper component placement.

• Station has not been selected

In this schematic, the engine has been started, but the clutch for this station has not been engaged. While the engine is running, pump (or system) pressure is always available at the modulation reduction valve spool; but, until pilot oil from the rotary selector spool is sent to the right (outer) end of the selector piston, there can be no valve movement and the clutch cannot be engaged.

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VALVE STATION CLUTCH FILLING

LOAD PISTON ORIFICE

118 • Station showing beginning of modulation • Selector spool movement begins modulation

This schematic shows the relative positions of the valve station components at the start of modulation before the clutch is fully engaged (primary pressure). Valve movement is initiated when pilot oil from the rotary selector spool moves the selector piston to the left as shown. Movement of the selector piston accomplishes two purposes: 1. The drain passage at the decay orifice is blocked. 2. The load piston springs are compressed.

• Clutch pressure increases

Compressing the load piston springs moves the reduction valve spool to the left against the force of the inner spring. This movement opens the supply passage (from the pump) and permits pressure oil to flow to the clutch. As the clutch fills, pressure oil opens the ball check valve and fills the slug chamber at the left end of the reduction valve spool. At the same time, oil flows through the load piston orifice and fills the chamber between the end of the load piston and the selector piston.

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The load piston orifice provides a pressure drop and time delay in the flow of oil to the load piston chamber. This condition helps control the rate of modulation. Filling the load piston chamber is made possible when the selector piston covers the drain passage at the decay orifice. • Clutch pressure maintained by reduction valve

The clutch pressure and the pressure in the slug chamber increase at the same rate. Just after the clutch is filled, the pressure in the slug chamber moves the reduction valve to the right. This movement restricts the flow of pressure oil to the clutch and briefly limits the increase of clutch pressure. The pressure in the load piston chamber then moves the load piston farther to the left. This movement increases the spring force and reopens the supply passage permitting the clutch pressure to again increase. This cycle continues until the load piston has moved completely to the left (against the stop). The clutch pressure is then at its maximum setting. During modulation, the reduction valve spool moves left and right while the load piston moves smoothly to the left.

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VALVE STATION CLUTCH ENGAGED

DRAIN

119 • Modulation cycle completed

The load piston has now moved completely to the left against the stop. The modulation cycle is completed and the clutch pressure is at its maximum setting. Because this is a modulation reduction valve, the maximum pressure setting of the clutch is lower than the system pressure. At the end of the modulation cycle, the pressure in the slug chamber moves the reduction valve a small distance to the right to restrict the flow of supply oil to the clutch. This is the "metering position" of the reduction valve spool. In this position, the valve maintains precise control of the clutch pressure.

• Clutch designed to leak small amount

During operation, an engaged clutch is designed to leak a relatively small but steady volume of oil. This leakage helps prevent high oil temperatures and provides additional lubrication for the planetary gears and bearings. As clutch leakage occurs, the clutch pressure and the pressure of the oil in the slug chamber will start to decrease. At this point, the load piston springs move the reduction valve spool a small distance to the left to open the supply passage. Pressure oil from the pump again enters the clutch circuit and replaces the leakage. Then, the clutch pressure in the slug chamber moves the spool back to the right thereby restricting the flow of supply oil to the clutch. This metering action continues during the entire time that the clutch is engaged.

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VALVE STATION CLUTCH DECAY

DECAY ORIFICE

DRAIN

120 • Clutch pressure decreases at controlled rate

During a shift, the pressure of the clutch (or clutches) being released does not immediately drop to zero. Instead, the clutch pressure decreases at a controlled rate. Restricting the rate of clutch pressure decay helps to maintain a positive torque at the transmission output shaft. This feature minimizes the effects of tire and axle "unwinding" and permits smoother shifts. An immediate drop in clutch pressure would permit a rapid deceleration of the power train components that remain connected to the differential during a shift.

• Decay orifice controls rate of clutch pressure decrease

When a clutch is released, the chamber at the right (outer) end of the selector piston is opened to drain through the lower chamber in the rotary selector spool. This condition permits the selector piston and load piston to move to the right as shown. Clutch pressure starts to decrease, but cannot drop to zero until the chamber between the load piston and the selector piston is drained. The only way that oil can flow out of this chamber is through the decay orifice which was uncovered when the selector piston moved to the right. As the load piston springs force the oil from the load piston chamber, the clutch pressure gradually decreases. When the load piston has moved completely to the right, the clutch pressure is zero.

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SHIFT MODULATION CYCLE

CLUTCH PRESSURE (PSI)

NORMAL SHIFT CYCLE

CLUTCH 1 418 365 CLUTCH 6 CLUTCH 3 265 COMPLETE CLUTCH ENGAGEMENT PRIMARY PRESSURE

INITIAL CLUTCH ENGAGEMENT

80 0

TIME

FILL TIME NORMAL CLUTCH SLIP

121 • Modulation cycle of clutches

This graph shows the clutch pressures as the ground speed increases and the transmission shifts into higher gears. Clutch 1 is being gradually released by the controlling effect of the decay orifice. At a certain point, clutch No. 3 is selected and the load piston orifice is controlling the modulation of engagement.

• Clutch overlap for smooth shifts

There is some overlap between the decay of the clutch being released and the clutch being engaged. This feature helps to minimize the unwinding motion of the power train and provide smooth shifts. Initial clutch engagement is the point where the operator can feel the transmission engaging a gear. Complete clutch engagement is the point where the operator feels the clutch stop slipping and the transmission clutch is fully engaged. Clutch pressures continue higher to ensure that the clutches do not slip. Normal clutch slip is the time between initial clutch engagement and complete clutch engagement.

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PRESSURE RESTRICTED LOAD PISTON ORIFICE SLOW MODULATION HIGH PRIMARY PRESSURE

COMPLETE CLUTCH ENGAGEMENT

LOW PRIMARY PRESSURE INITIAL CLUTCH ENGAGEMENT

NORMAL PRIMARY PRESSURE

0

TIME

HIGH PRIMARY PRESSURE HARSH SHIFT NORMAL CLUTCH SLIP

SHIFT MODULATION PROBLEMS

LOW PRIMARY PRESSURE CLUTCH SLIPPING RESTRICTED LOAD PISTON ORIFICE CLUTCH SLIPPING

122 • Three shift conditions: 1. High primary pressure 2. Low primary pressure 3. Slow modulation

This graph shows the effects of the following conditions: 1. High primary pressure - Shorter engagement time which causes harsh shifts of the power train components and increases the maximum clutch pressure. 2. Low primary pressure - Longer engagement time which causes the plates and discs to slip more before the engagement pressure holds them together. Maximum clutch pressure is also lower and may cause slippage during conditions of heavy loading. 3. Slow modulation - This effect is very similar to the low primary pressure, but it can be caused by a partially plugged load piston orifice. The maximum clutch pressure would be within specifications.

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777D TRANSMISSION HYDRAULIC SYSTEM TRANSMISSION CHARGING FILTER

PUMP DRIVE

HOIST PUMP

TRANSMISSION OIL COOLER

STEERING PUMP

TRANSMISSION SCAVENGE PUMP

TRANSMISSION CHARGE PUMP

MAGNETIC SCAVENGE SCREEN

123 • Transmission hydraulic system • Two section pump: - Transmission scavenge - Transmission charging

The two section transmission pump is mounted on the rear of the pump drive, which is located inside the right frame near the torque converter. The two sections are: - Transmission scavenge - Transmission charging The transmission scavenge section pulls oil from the bottom of the transmission case through the magnetic screen located below the pump. The scavenged oil from the transmission flows through the transmission oil cooler and returns to the transmission tank. The transmission charging section pulls oil from the transmission tank. Charging oil flows from the pump through a transmission charging filter to the hydraulic controls in the transmission.

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2

1

3

124

Rear Axle 1. Differential magnetic inspection plug

Check the differential oil level by removing the magnetic inspection plug (1). The oil should be level with the bottom of the fill plug opening. The magnetic inspection plug should be removed at regular intervals and checked for metal particles.

2. Rear axle breather

Inspect the condition of the rear axle breather (2) at regular intervals. The breather prevents pressure from building up in the axle housing. Excessive pressure in the axle housing can cause brake cooling oil to leak through the Duo-Cone seals in the wheel brake assemblies.

3. Differential carrier thrust pin cover

A differential carrier thrust pin is located behind the small cover (3). The thrust pin prevents movement of the differential carrier during high thrust load conditions.

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125

• Differential

Shown is the differential removed from the rear axle housing. The differential is located in the rear axle housing behind the transmission. Power flows from the transmission to the differential. The differential divides the power to the right and left axle shafts. Torque is transmitted equally from the differential through the two axle shafts to the final drives. The differential adjusts the speed of the axle shafts for vehicle cornering, therefore, the power delivered to the axle shafts is unequal during cornering.

• Differential carrier thrust pin contact location (arrow)

The differential thrust pin contacts the differential carrier at the location shown (arrow). When high thrust loads are transmitted from the differential pinion to the differential ring gear, the carrier tries to move away from the pinion. The thrust pin prevents movement of the differential carrier during high thrust load conditions.

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126

Transmission/Chassis Electronic Control System • Transmission/Chassis ECM (arrow)

The Transmission/Chassis ECM (arrow) is located in the compartment at the rear of the cab. The transmission control used in the earlier 777D trucks is referred to as the second generation Electronic Programmable Transmission Control (EPTC II). The transmission control used in the 777D Update trucks performs the transmission control functions, plus some other machine functions (hoist and secondary steering control). Because of the added functionality of the control, it is now referred to as the "Transmission/Chassis ECM."

• Transmission/Chassis ECM - No diagnostic window - Diagnostics and programming require ECAP or ET • Transmission/Chassis ECM looks like Engine ECM

The Transmission/Chassis ECM does not have a diagnostic window as in the EPTC II. Diagnostic and programming functions must be performed with an Electronic Control Analyzer Programmer (ECAP) or a laptop computer with the Electronic Technician (ET) software installed. ET is the tool of choice because the Transmission/Chassis ECM can be reprogrammed with a "flash" file using the WinFlash application of ET. The ECAP cannot upload "flash" files. The Transmission/Chassis ECM appears identical to the Engine ECM with two 40-pin connectors, but the Transmission/Chassis ECM does not have fittings for cooling fluid. Also, the Transmission/Chassis ECM has no access plate for a personality module.

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TRANSMISSION/CHASSIS ELECTRONIC CONTROL SYSTEM

INPUT COMPONENTS

OUTPUT COMPONENTS

ECM LOCATION CODE

CAT DATA LINK ELECTRONIC SERVICE TOOL

SHIFT LEVER POSITION SWITCH

ENGINE ECM BRAKE ECM

TRANSMISSION GEAR SWITCH °C kPaMiles KM RPM Liter SERV CODE X10

TRANSMISSION OUTPUT SPEED SENSOR

CATERPILLAR MONITORING SYSTEM

. ..

UPSHIFT SOLENOID

ENGINE OUTPUT SPEED SENSOR

DOWNSHIFT SOLENOID

SERVICE/RETARDER BRAKE PRESSURE SWITCH

LOCKUP SOLENOID PARKING/SECONDARY BRAKE PRESSURE SWITCH

BACK-UP ALARM RELAY

BODY UP SWITCH

SECONDARY STEERING RELAY

KEY START SWITCH

STARTER RELAY

LOW STEERING PRESSURE SWITCH BODY RAISE SOLENOID HOIST LEVER POSITION SENSOR BODY LOWER SOLENOID EXHAUST DIVERTER SWITCH

BODY UP DASH LAMP

127 • Transmission/Chassis ECM shifts transmission electronically

The purpose of the Transmission/Chassis ECM is to determine the desired transmission gear and energize solenoids to shift the transmission up or down as required based on information from both the operator and machine.

• Transmission/Chassis ECM inputs

The Transmission/Chassis ECM receives information (electrical signals) from various input components such as the shift lever switch, Transmission Output Speed (TOS) sensor, transmission gear switch, body up switch and the hoist lever sensor. Based on the input information, the Transmission/Chassis ECM determines when the transmission should upshift, downshift, engage the lockup clutch or limit the transmission gear. These actions are accomplished by sending electrical signals to various output components.

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Output components include the upshift, downshift and lockup solenoids, the back-up alarm and others. The Transmission/Chassis ECM also provides the service technician with enhanced diagnostic capabilities through the use of onboard memory, which stores possible diagnostic codes for retrieval at the time of service.

• Benefits of electronic communication

The Engine ECM, the Brake ECM [Automatic Retarder Control (ARC) and Traction Control System (TCS)], the Caterpillar Monitoring System and the Transmission/Chassis ECM all communicate through the CAT Data Link. Communication between the electronic controls allows the sensors of each system to be shared. Many additional benefits are provided, such as Controlled Throttle Shifting (CTS). CTS occurs when the Transmission/Chassis ECM signals the Engine ECM to reduce engine fuel during a shift to lower stress to the power train.

• Transmission/Chassis ECM controls hoist and secondary steering

The Transmission/Chassis ECM is also used to control the hoist and secondary steering system on the 777D Update trucks.

• Service tool diagnostic and programming functions

Some of the diagnostic and programming functions that the service tools can perform are:

The Electronic Control Analyzer Programmer (ECAP) and the Electronic Technician (ET) Service Tools can be used to perform several diagnostic and programming functions.

- Display the real time status of the input and output parameters - Display the internal clock hour reading - Display the number of occurrences and the hour reading of the first and last occurrence for each logged diagnostic code and event - Display the definition for each logged diagnostic code and event - Display load counters - Display the lockup clutch engagement counter - Display the transmission gear shift counter - Program the top gear limit and the body up gear limit - Upload new Flash files

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INSTRUCTOR NOTE: In the following slides, only some of the input and output components of the Transmission/Chassis ECM will be shown. Some of the Transmission/Chassis ECM input and output components are shown during the discussion of other systems. See the following slide numbers: 127. ECM location code 128. Shift lever position switch 129. Transmission gear switch 130. Transmission output speed sensor 63. Engine output speed sensor 131. Service/Retarder brake pressure switch 131. Parking/Secondary brake pressure switch 132. Body up switch 37. Key start switch 140. Low steering pressure switch 148. Hoist lever position sensor N/A. Exhaust diverter switch (not shown) 55. Electronic service tool 60. Engine ECM 196. Brake ECM 41. Caterpillar Monitoring System 129. Upshift solenoid 129. Downshift solenoid 105. Lockup solenoid 53. Back-up alarm relay N/A. Starter relay (not shown) 54 and 140. Secondary steering relay 152. Body raise solenoid 152. Body lower solenoid 44. Body up dash lamp • ECM location code

The "ECM location code" is similar to the "harness code" designation referred to on earlier electronic controls. The ECM location code consists of three pins (J1-21, 22 and 38) in the ECM that can be either OPEN or GROUNDED. The combination of OPEN or GROUNDED pins determines which function the ECM will perform. For example, if pin J1-22 is GROUNDED and pins J1-21 and J1-38 are OPEN, that ECM will function as the Transmission/Chassis ECM. When connecting a laptop with ET software, ET will also automatically show this ECM as the Transmission/Chassis ECM. Pin J1-28 is also part of the ECM location code. Pin J1-28 receives + Battery voltage to enable the location code parameter. The ECM location code is especially important when uploading new "flash files." Without the location code, ET would not know which ECM to FLASH.

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2 3

1

128 1. Shift lever switch

The shift lever (also referred to as the "cane" or "gear selector") switch (1) is located inside the cab in the shift console and provides input signals to the Transmission/Chassis ECM. The shift lever switch controls the desired top gear selected by the operator.

• Shift lever switch operation

The shift lever switch input signals are transmitted through six wires. Five of the six wires provide a code to the Transmission/Chassis ECM. The code is unique for each position of the switch. Each switch position will result in two of the five wires sending a ground signal to the Transmission/Chassis ECM. The other three wires will remain open (ungrounded). The pair of grounded wires is unique for each lever position. The sixth wire is known as the "ground verify" wire, which is normally grounded. The ground verify wire is used by the Transmission/Chassis ECM to verify that the lever switch is connected to the Transmission/Chassis ECM. The ground verify wire allows the Transmission/Chassis ECM to distinguish between the loss of the lever switch signals and a condition in which the lever switch is between detent positions.

• Shift lever diagnostics

To view the shift lever switch positions or diagnose problems with the switch, use the monitoring system display window and observe the gear lever status. As the shift lever is moved through the detent positions, the gear lever status will display the corresponding lever position shown on the shift console.

2. Adjustment nuts

The position of the shift lever can be changed to obtain better alignment with the gear position numbers on the shift console by loosening the three nuts (2) and rotating the lever. The position of the shift lever switch can also be adjusted with the two screws (3).

3. Adjustment screws

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3

2

1

129 1. Transmission gear switch - Switch type input

The transmission gear switch (1) provides input signals to the Transmission/Chassis ECM. The transmission gear switch inputs (also referred to as the actual gear inputs) are comprised of six wires. Five of the six wires provide a code to the ECM. The code is unique for each position of the transmission gear switch. Each transmission gear switch position will result in two of the five wires sending a ground signal to the ECM. The other three wires will remain open (ungrounded). The pair of grounded wires is unique for each gear position. The sixth wire is known as the "ground verify" wire, which is normally grounded. The ground verify wire is used by the ECM to verify that the transmission gear switch is connected to the transmission control. The ground verify wire allows the ECM to distinguish between the loss of the transmission gear switch signals and a condition in which the transmission gear switch is between gear detent positions.

• Gear switch is HallEffect type switch

Earlier transmission gear switches use a wiper contact assembly that does not require a power supply to Pin 4 of the switch. Present transmission gear switches are Hall-Effect type switches. A power supply is required to power the switch. A small magnet passes over the Hall cells which then provide a non-contact position switching capability. The Hall-Effect type switch uses the same 24-Volt power supply used to power the Transmission/Chassis ECM.

2. Upshift solenoid

The solenoid outputs provide + Battery voltage to the upshift solenoid (2) or the downshift solenoid (3) based on the input information from the operator and the machine. The solenoids are energized until the transmission actual gear switch signals the Transmission/Chassis ECM that a new gear position has been reached.

3. Downshift solenoid

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130 • TOS sensor (arrow)

The Transmission Output Speed (TOS) Sensor (arrow) is located on the transfer gear housing on the input end of the transmission. Although the sensor is physically located near the input end of the transmission, the sensor is measuring the speed of the transmission output shaft. The sensor is a Hall-Effect type sensor. Therefore, a power supply is required to power the sensor. The sensor receives 10 Volts from the Transmission/Chassis ECM. The sensor output is a square wave signal of approximately 10 Volts amplitude. The frequency in Hz of the square wave is equal to twice the output shaft rpm. The signal from this sensor is used for automatic shifting of the transmission. The signal is also used to drive the speedometer and as an input to other electronic controls.

• Engine rpm is calculated for shift points

The Transmission/Chassis ECM uses the TOS sensor to determine when to shift, but the shifts always occur at a precise engine rpm. The engine rpm is known because the Transmission/Chassis ECM knows the gear ratios of the transfer gears, each gear range of the transmission, the differential and the final drives. The ECM also estimates the circumference of the tires. The ECM uses the gear ratios and tire circumference to calculate the engine rpm for any ground speed.

• 8T5200 Signal Generator/Counter

An 8T5200 Signal Generator/Counter can be used to shift the transmission during diagnostic tests. Disconnect the harness from the speed sensor and attach the Signal Generator to the harness. Depress the ON and HI frequency buttons. Start the engine and move the shift lever to the highest gear position. Rotate the frequency dial to increase the ground speed, and the transmission will shift.

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1

3

4 2

131 1. Service/retarder brake switch

• Service/retarder brakes engaged: - Raises shift points - Eliminates anti-hunt timer

The service/retarder brake switch (1) is located in the compartment behind the cab. The switch is normally closed and opens when service/retarder brake air pressure is applied. The switch has two functions for the Transmission/Chassis ECM: - Signals the Transmission/Chassis ECM to use elevated shift points, which provide increased engine speed during downhill retarding for increased oil flow to the brake cooling circuit. - Signals the Transmission/Chassis ECM to allow rapid shifting during braking by overriding the anti-hunt timer. A diagnostic code is stored if the Transmission/Chassis ECM does not receive a closed (ground) signal from the switch within seven hours of operation time or an open signal from the switch within two hours of operation time.

• Service/retarder switch used as TCS input

The Traction Control System (TCS) also uses the service/retarder brake switch as an input through the CAT Data Link (see Slide No. 201).

STMG 721 01/00 2. Parking/secondary brake switch

• Parking/secondary brakes engaged: - Eliminates anti-hunt timer - Signals parked machine

•

Back-up alarm relay

• Hoist lever sensor - Reverse inhibitor operation

- 162 -

The parking/secondary brake switch (2) is in the parking/secondary brake air pressure line. The normally open switch is closed during the application of air pressure. The purpose of the switch is to signal the Transmission/Chassis ECM when the parking/secondary brakes are ENGAGED. Since the parking/secondary brakes are spring engaged and pressure released, the parking/secondary brake switch is closed when the brakes are RELEASED and opens when the brakes are ENGAGED. This signal is used to override the anti-hunt timer for rapid downshifting and is used to sense when the machine is parked. A diagnostic code is stored if the Transmission/Chassis ECM does not receive a closed (ground) signal from the switch within seven hours of operation time or an open signal from the switch within one hour of operation time. The back-up alarm relay (see Slide No. 53) is also located behind the cab. When the operator moves the shift lever to REVERSE, the Transmission/Chassis ECM provides a signal to the back-up alarm relay, which turns ON the back-up alarm. Another input to the Transmission/Chassis ECM is the hoist lever sensor (see Slide No. 148). The main function of the hoist lever sensor is to raise and lower the body, but it is also used to NEUTRALIZE the transmission. If the transmission is in REVERSE when the body is being raised, the hoist lever sensor is used to shift the transmission to NEUTRAL. The transmission will remain in NEUTRAL until: - The hoist lever is moved into the HOLD or FLOAT position. - The shift lever has been cycled into and out of NEUTRAL.

3. System air pressure sensor 4. Brake light switch

• Lockup solenoid

The system air pressure sensor (3) and the brake light switch (4) are also located in the compartment behind the cab. The low air pressure sensor provides an input signal to the Brake ECM. The Brake ECM sends a signal to the Caterpillar Monitoring System, which informs the operator of the system air pressure condition. The Transmission/Chassis ECM provides +24 Volts to the torque converter lockup solenoid to control the lockup clutch pressure (see Slide No. 105). When the lockup solenoid is energized, the lockup valve supplies oil to ENGAGE the lockup clutch in the torque converter.

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3 2

1

4

132 1. Body up switch 2. Magnet

The body up switch (1) is located on the frame near the body pivot pin. This magnetic switch is normally open. When the body is raised, a magnet (2) mounted on the body passes the switch and causes the switch to close. The resulting ground signal is sent to the Transmission/Chassis ECM. This signal is used to limit the top gear into which the transmission will shift when the body is up. The body up top gear value is programmable from FIRST to THIRD utilizing the ECAP or ET Service Tool. The ECM comes from the factory with this value set to FIRST gear. When driving away from a dump site, the transmission will not shift past FIRST gear until the body is down. If the transmission is already above the set limit gear when the body is raised, no limiting action will take place.

• Body up signal used for hoist SNUB control

The body up switch signal is also used to control the SNUB position of the hoist control valve. As the body is lowered and the magnet passes the body up switch, the Transmission/Chassis ECM signals the hoist lower solenoid to move the hoist valve spool to the SNUB position. In the SNUB position, the body float speed is reduced to prevent the body from making hard contact with the frame.

• Body up switch input provides several functions

The body up switch input provides the following functions: - Body up gear limiting - Body up sound reduction - Hoist snubbing - Lights the body up dash lamp - Signals a new load count (after 10 seconds in the RAISE position)

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• Body up diagnostic code

A diagnostic code occurs if the Transmission/Chassis ECM does not receive a closed (ground) signal from the switch within four hours of operation time or an open signal from the switch within one hour of operation time.

3. Body stringer

The body up switch must be adjusted properly for all of the functions to operate correctly. To adjust the body up switch, raise the body until the distance between the front of the stringer (3) and the main frame (4) is 360 mm (14.2 in.). Install blocks to prevent the body from moving during the adjustment.

4. Main frame

• Body up switch adjustment

Position the body up switch bracket (bracket has slotted holes for adjustment) on the main frame with a 4 ± 1 mm (.18 ± .04 in.) gap between the magnet and the switch. Tighten the bracket mounting bolts. Raise the switch on the bracket until the amber LED turns ON. Tighten the switch mounting bolts, remove the blocks and check for proper operation.

• Body up switch LED's

Two LED's are located on the body up switch. The green LED indicates that battery power is present. The amber LED indicates that the switch is closed (grounded).

• SNUB adjustment fine tuning

The body position switch can be raised or lowered slightly in the bracket notches to start the SNUB feature sooner or later.

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TRANSMISSION/CHASSIS ECM SYSTEMS CONTROLLED BY ECM • TRANSMISSION SHIFTING • TOP GEAR LIMIT • REVERSE INHIBITOR • STARTER PROTECTION • NEUTRAL START

• TORQUE CONVERTER LOCKUP • BODY UP GEAR LIMIT • BODY HOIST • ENGINE OIL PRE-LUBRICATION • FAIL IN GEAR PROTECTION

• SHIFT COUNTER • LOAD COUNTER • SECONDARY STEERING

• CONTROL THROTTLE SHIFTING (CTS) • DIRECTIONAL SHIFT MANAGEMENT • NEUTRAL COAST INHIBITING

• BACKUP ALARM • ANTI-HUNT

• ENGINE OVERSPEED PROTECTION

133 Besides controlling the Transmission Shifting and Torque Converter Lockup, the Transmission/Chassis ECM also controls other functions such as Engine Overspeed Protection, Control Throttle Shifting (CTS), Directional Shift Management, Top Gear Limit and Fail In Gear Protection. - Top Gear Limit

Top Gear Limit: The top gear limit is FIELD programmable from FOURTH to SEVENTH by use of the ET or ECAP service tool. The Transmission/Chassis ECM comes from the factory set to the maximum gear available (SEVENTH GEAR). The transmission will NEVER shift to a gear above the programmed top gear.

- Body Up Gear Limit

Body Up Gear Limit: (see Slide No. 132)

- Reverse Inhibitor

Reverse Inhibitor: (see Slide No. 40)

- Body Hoist

Body Hoist: (see Hoist System)

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- Starter Protection

Starter Protection: - The Transmission/Chassis ECM will only energize the Starter Relay if engine speed is 0 rpm. - The starter is disengaged when engine rpm is greater than 300 rpm. - If system voltage is greater than 36 volts, which is possible during abusive jump-starting situations, the start output will not be energized in order to protect the machine starting circuit.

- Engine Oil PreLubrication

Engine Oil Pre-Lubrication: (see Slide No. 69)

- Neutral Start

Neutral Start: The Engine Start function is controlled by the Engine ECM and the Transmission/Chassis ECM. The Engine ECM provides a signal to the Transmission/Chassis ECM regarding the engine speed and the condition of the engine pre-lubrication system. The Transmission/Chassis ECM will energize the starter relay only when: - The shift lever is in NEUTRAL. - The parking brake is ENGAGED. - The engine speed is 0 rpm. - The engine pre-lubrication cycle is complete or turned OFF.

- Fail In Gear Protection

Fail In Gear Protection: Prevents shifts to a gear that is not appropriate for the current ground speed (engine overspeed protection). If the Transmission/Chassis ECM loses the ground speed, shift lever switch or actual gear switch signals, the ECM will de-energize the upshift, downshift and lockup solenoids. De-energizing the solenoids will keep the transmission in the current gear. If the signals return, the ECM will shift the transmission to the correct gear for the current ground speed.

- Shift Counter

Shift Counter: A complete histogram of all shift events can be accessed with the ECAP or ET service tool. Shift counter information can be used to predict upcoming transmission or torque converter lockup clutch service. The control will log a maximum of 1.2 million counts for each transmission gear position. To log an additional count, the transmission gear switch position must change and hold the new position for .5 seconds. The control will log a maximum of 12 million counts for the torque converter lockup clutch counter.

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Control Throttle Shifting (CTS): Controlled throttle shifting is used to smooth shifting and reduce driveline stress during all automatic transmission shifts. The Transmission/Chassis ECM sends a signal to the Engine ECM through the CAT Data Link during each transmission shift to reduce or increase the fuel flow, which reduces the torque during a shift. During automatic upshifts, if the throttle position is at 100%, the Transmission/Chassis ECM sends a signal to the engine control to momentarily reduce the "Desired Engine Speed." During automatic downshifts, if the throttle position is at 0%, the Transmission/Chassis ECM sends a signal to the Engine ECM to momentarily increase the "Desired Engine Speed."

- Load Counter

Load Counter: (see Slide No. 132) Resettable Load Count: The Transmission/Chassis ECM will log a Resettable Load Count. The number of loads since last re-set by using the Caterpillar Monitoring System, ET or ECAP service tool can be viewed. The number of loads is calculated as equal to the number of times the body has been raised. The Body is considered RAISED if the Body Up Switch is in the RAISED position for more than 10 seconds. Permanent Load Count: The Transmission/Chassis ECM will log a Permanent Load Count. The permanent load count cannot be re-set. The total number of loads accumulated since the machine was put into production can be viewed using the Caterpillar Monitoring System, ET or ECAP service tool.

- Directional Shift Management

Directional Shift Management: Directional shift management is used to reduce driveline stress during directional shifts. The Transmission/ Chassis ECM sends a signal to the Engine ECM during directional shifts to reduce the fuel flow, which reduces the torque during a shift. If the operator shifts from NEUTRAL to FIRST or REVERSE with the engine speed above 1350 rpm, a signal is sent to the Engine ECM through the CAT Data Link and "Desired Engine Speed" is reduced to LOW IDLE.

- Secondary Steering

Secondary Steering: (see Slide No. 140)

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Neutral Coast Inhibiting: When the transmission is in gear and the shift lever is placed in NEUTRAL, the machine will remain in gear until the machine travel speed has been reduced from the lL to lC shift point (Lockup to Converter drive) [(approximately 8 km/h (5 mph)]. At approximately 8 km/h (5 mph) the Transmission/Chassis ECM will shift the transmission to NEUTRAL. Keeping the transmission in gear above 8 km/h (5 mph) will discourage high-speed coasting in NEUTRAL. High-speed coasting in NEUTRAL can reduce transmission life. This function does not prevent coasting in NEUTRAL, but makes it more difficult. The operator CAN COAST in NEUTRAL if he starts down a hill in NEUTRAL and travel speed is below 8 km/h (5 mph). If the operator does coast in NEUTRAL, at speeds above 12 mph, engine speed will increase to 1300 rpm and an event will be logged by the Transmission/Chassis ECM as "Coasting In Neutral". This information can be reviewed using the ECAP or ET Service Tool. Shifts to REVERSE from a Forward Gear are inhibited until travel speed is below 4.8 km/h (3 mph).

- Back-up Alarm

Back-up Alarm: (see Slide No. 131)

- Engine Overspeed Protection

Engine Overspeed Protection: If the engine speed (based on machine travel speed and gear) increases to a pre-determined level which warrants action, the Transmission/Chassis ECM will upshift the transmission ONE gear position past the operator's selection to protect the engine from overspeed. If the transmission is already in the top gear, the Transmission/Chassis ECM will shift the torque converter into CONVERTER DRIVE.

- Anti-Hunt

Anti-Hunt: During normal shifting, the ECM does not allow a turnaround shift for 2.3 seconds after a shift occurs. A turnaround shift is an opposite shift from the previous shift. For example, a downshift is prevented for 2.3 seconds after an upshift and an upshift is prevented for 2.3 seconds after a downshift. This turnaround time delay allows conditions to stabilize before an opposite shift. The delay prevents hunting between gears. The ECM overrides the turnaround time delay when the operator applies the brakes. Downshifts now occur immediately as a result of the decreasing transmission output speed. This function is provided in case the operator is required to make a sudden stop. The service/retarder brakes also provide elevated shift points in order to increase brake cooling.

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TRANSMISSION/CHASSIS ECM LOGGED EVENTS • COASTING IN NEUTRAL • TRANSMISSION ABUSE • ENGINE OVERSPEED • MACHINE OVERSPEED

134 • Coasting In Neutral

Coasting In Neutral: If the operator coasts in NEUTRAL at speeds above 19.3 km/h (12 mph), engine speed will increase to 1300 rpm and an event will be logged by the Transmission/Chassis ECM as a "Coasting in Neutral" event.

• Transmission Abuse

Transmission Abuse: If the operator shifts from NEUTRAL to FIRST or REVERSE with the engine speed above 1350 rpm, the "Desired Engine Speed" will be momentarily reduced to low idle, and an event will be logged by the Transmission/Chassis ECM as a "Transmission Abuse" event.

• Engine Overspeed

Engine Overspeed: If the operator positions the shift lever in a position lower than the maximum gear available, at 2100 rpm an action lamp will illuminate and an alarm will sound. If engine speed exceeds 2300 rpm, the Transmission/Chassis ECM will signal for a shift to a higher gear (one gear only) to protect the engine. After the shift is made, if engine speed exceeds 2300 rpm again, an event will be logged by the Transmission/Chassis ECM as an "Engine Overspeed" event.

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Machine Overspeed: If the operator positions the shift lever in the maximum gear available position, an action lamp will illuminate and an alarm will sound at 2100 rpm. If engine speed exceeds 2300 rpm, the Transmission/Chassis ECM will unlock the torque converter to protect the engine. After the torque converter is unlocked, if engine speed again exceeds 2300 rpm, an event will be logged by the Transmission/Chassis ECM as a "Machine Overspeed" event. A Machine Overspeed should be considered as an Engine Overspeed.

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135

STEERING SYSTEM This section of the presentation explains the operation of the steering system. As on other Caterpillar Off-highway Trucks, the steering system uses hydraulic force to change the direction of the front wheels. The system has no mechanical connection between the steering wheel and the steering cylinders. • Load sensing, pressure compensated - Requires less horsepower

The 777D Update trucks use a load sensing, pressure compensated steering system which is a substantial change from the steering system used on the earlier 777D trucks. Minimal horsepower is used by the steering system when the truck is traveling in a straight path. Steering hydraulic horsepower requirements depend on the amount of steering pressure and flow required by the steering cylinders. With the engine removed and looking from the front of the truck, the steering system components shown are:

1. Steering tank 2. Steering pump 3. Steering valve 4. Secondary steering motor and pump

- Steering tank (1) - Steering pump (2) - Steering valve (3) - Secondary steering motor and pump (4)

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136

• Steering system tank

The steering system tank is located on the right platform

1. Steering system oil level sight gauge

Check the steering system oil level at the sight gauge (1).

2. Steering system oil filter

The steering system oil filter (2) is located on the side of the steering tank.

3. Case drain oil filter

The steering system uses a pressure compensated piston type pump. Case drain oil from the steering pump returns to the hydraulic tank through a case drain filter (3) on the side of the steering tank.

4. Steering tank pressure release button and breather

Before removing the cap to add oil to the steering system, depress the pressure release button (4) on the breather to release any remaining pressure from the tank.

5. Steering system S•O•S tap

Steering system oil samples can be taken from the Scheduled Oil Sampling (S•O•S) tap (5) located in the case drain return hose.

• Filter bypass valves

The steering system filter base and the case drain filter base have bypass valves that allow the steering oil to bypass the filters if they are plugged.

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137 • Steering pump 1. High pressure cutoff valve - Main steering system relief

The 777D Update trucks are equipped with a load sensing, pressure compensated, piston-type pump. The steering pump operates only when the engine is running and provides the necessary flow of oil for steering system operation. The steering pump contains a load sensing controller with two valves. The high pressure cutoff valve (1) functions as the primary steering system relief valve.

• Steering system primary relief adjustment

To adjust the primary steering system pressure setting (high pressure cutoff), remove the cover nut, loosen the locknut and turn the adjusting screw IN to increase the pressure or OUT to decrease the pressure. The primary steering system pressure setting is 23425 ± 345 kPa (3400 ± 50 psi). To verify the new pressure setting, install a gauge on the pressure tap (shown in Slide No. 140). Operate the truck in NEUTRAL with the engine at HIGH IDLE, and turn the steering wheel hard against the stops to the left or right.

2. Flow compensator valve

The flow compensator valve (2) is used to adjust the low pressure standby setting. When the truck is traveling in a straight path, virtually no flow or pressure is required to the steering cylinders, and the pump destrokes to low pressure standby.

- Low pressure standby

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• Low pressure standby adjustment

To adjust the low pressure standby setting, remove the cover nut, loosen the locknut and turn the adjusting screw IN to increase the pressure or OUT to decrease the pressure. The low pressure standby setting should be between 2070 and 2950 kPa (300 and 430 psi). To verify the new pressure setting, install a gauge on the pressure tap (shown in slide No. 140). Operate the truck in NEUTRAL with the engine at HIGH IDLE, and DO NOT turn the steering wheel.

3. Load sensing signal pressure hose

Load Sensing (LS) signal pressure from the Hand Metering Unit (HMU) (see Slide No. 142) enters the spring chamber of the flow compensator valve through the hose (3).

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LOAD SENSING PRESSURE FROM HMU

TO STEERING VALVE AND HMU

HIGH PRESSURE CUTOFF VALVE

STEERING PUMP LOW PRESSURE STANDBY

ACTUATOR PISTON

FLOW COMPENSATOR LOAD SENSING CONTROLLER SWASHPLATE PISTON CASE DRAIN FILTER

138 • Low pressure standby

When the truck is traveling in a straight path, the steering cylinders require virtually no flow or pressure. The HMU provides a very low pressure load sensing signal to the flow compensator in the load sensing controller. Pump oil (at low pressure standby) flows to the swashplate piston and past the lower end of the displaced flow compensator spool to the actuator piston. The actuator piston has a larger surface area than the swashplate piston. The oil pressure at the actuator piston overcomes the spring force and the oil pressure in the swashplate piston and moves the swashplate to destroke the pump. The pump is then at minimum flow, low pressure standby.

• Low pressure standby setting

Pump output pressure is equal to the setting of the flow compensator plus the pressure required to compensate for system leakage. The low pressure standby setting should be between 2070 and 2950 kPa (300 and 430 psi).

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LOAD SENSING PRESSURE FROM HMU

TO STEERING VALVE AND HMU

STEERING PUMP MAXIMUM FLOW

HIGH PRESSURE CUTOFF VALVE ACTUATOR PISTON

FLOW COMPENSATOR LOAD SENSING CONTROLLER SWASHPLATE PISTON CASE DRAIN FILTER

139 • Steering pump at maximum flow

During a turn, when steering pressure and flow are required, pressure increases in the HMU load sensing signal line. The pressure in the signal line is equal to the pressure in the steering cylinders. The pump load sensing controller is spring biased to vent the actuator piston pressure to drain. Venting pressure from the load sensing controller and the actuator piston positions the spring biased swashplate to maximum displacement (maximum flow). As pressure increases in the HMU load sensing signal line, pump supply pressure is sensed on both ends of the flow compensator. When pressure is present on both ends of the flow compensator, the swashplate is kept at maximum angle by the force of the spring in the pump housing and pump discharge pressure on the swashplate piston. The pistons reciprocate in and out of the barrel and maximum flow is provided through the outlet port. Since the pump is driven by the engine, engine rpm also affects pump output.

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140 1. Steering pressure switch

Steering oil flows from the pump to the steering valve located on the frame behind the right front suspension cylinder. A steering pressure switch (1) monitors the output of the steering pump. The steering pressure switch provides input signals to the Transmission/Chassis ECM, and the Caterpillar Monitoring System informs the operator of the condition of the steering system. A steering system warning is displayed if the pressure in the steering system drops below 700 ± 100 kPa (100 ± 15 psi).

2. Pressure reducing valve

The steering pressure switch cannot tolerate high steering system pressures. A pressure reducing valve (2) reduces the steering system pressure to the steering pressure switch. The setting of the pressure reducing valve is 2600 + 500 - 200 kPa (375 + 70 - 30 psi). To check the setting of the pressure reducing valve, remove the steering pressure switch and install a gauge in the switch port. Operate the truck in NEUTRAL with the engine at LOW IDLE and turn the steering wheel hard against the stops to the left or right.

• Secondary steering

If the steering pressure switch signals the Transmission/Chassis ECM that the steering system pressure is low, the ECM will energize the secondary steering relay located behind the cab. The secondary steering relay will then energize a second larger relay located on the frame above the steering valve, which will then turn ON the secondary steering motor (3). Secondary steering supply oil flows to the steering valve from the secondary steering pump through the small hose on the right side of the valve.

3. Secondary steering motor

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4. Secondary steering primary relief valve plug

The primary relief valve for the secondary steering circuit is in the secondary steering pump load sensing valve. The setting of the relief valve is 16880 ± 345 kPa (2450 ± 50 psi). The relief valve is accessible through the small allen head plug (4).

• Secondary steering primary relief valve adjustment

To check the setting of the secondary steering primary relief valve, do not start the truck. Turn ON the key start switch and depress the secondary steering switch located on the dash (see Slide No. 46). Turn the steering wheel hard to the left or right while the secondary steering pump is running. Secondary steering system pressures can be measured at the steering system pressure tap (see Slide No. 141).

5. Secondary steering back-up relief valve

Two relief valves are located on the left side of the steering valve. The top relief valve (5) is a back-up relief valve for the secondary steering system. The secondary steering back-up relief valve protects the secondary steering system if the relief valve on the secondary steering pump malfunctions. The setting of the secondary steering back-up relief valve is 20700 ± 400 kPa (3000 ± 60 psi).

• Secondary steering back-up relief valve adjustment

To check the setting of the secondary steering back-up relief valve, increase the setting of the relief valve in the secondary steering pump load sensing valve. Count the number of turns made to the adjustment screw so the valve can be returned to its original setting. Loosen the locknut on the secondary steering back-up relief valve, and turn the adjusting screw IN to increase the pressure or OUT to decrease the pressure. To verify the new pressure setting, do not start the truck. Turn ON the key start switch and depress the secondary steering switch located on the dash (see Slide No. 46). Turn the steering wheel hard to the left or right while the secondary steering pump is running.

6. Primary steering back-up relief valve

The lower relief valve (6) is a back-up relief valve for the primary steering system. The primary steering back-up relief valve protects the primary steering system if the high pressure cutoff valve on the steering pump malfunctions. The setting of the primary steering back-up relief valve is 26000 ± 400 kPa (3775 ± 60 psi). Primary steering pressure is first controlled by the high pressure cutoff valve located on the steering pump. The setting of the high pressure cutoff valve on the steering pump is 23425 ± 345 kPa (3400 ± 50 psi).

• Primary steering back-up relief valve adjustment

To check the setting of the primary steering back-up relief valve, increase the setting of the high pressure cutoff valve on the steering pump. Count the number of turns made to the adjustment screw so the valve can be returned to its original setting. Loosen the locknut on the primary steering back-up relief valve, and turn the adjusting screw IN to increase the pressure or OUT to decrease the pressure. To verify the new pressure setting, operate the truck in NEUTRAL with the engine at LOW IDLE and turn the steering wheel hard against the stops to the left or right.

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• Check valve plugs 1. Secondary check valve 2. Primary check valve 3. Steering system pressure tap

Shown is a front view of the steering valve. Located behind the two plugs are two check valves. The check valves are used to separate the primary and secondary steering systems. The secondary check valve (1) is behind the left plug, and the primary check valve (2) is behind the right plug. Steering system pressures can be measured at the steering system pressure tap (3).

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142 1. HMU

The Hand Metering Unit (HMU) (1) is located at the base of the steering column behind a cover at the front of the cab. The HMU is connected to the steering wheel and controlled by the operator.

• Meters oil to steering cylinders

The HMU meters the amount of oil sent to the steering cylinders by the speed at which the steering wheel is turned. The faster the HMU is turned, the higher the flow sent to the steering cylinders, and the faster the wheels will change direction.

• Q-amp steering system

The steering system is referred to as "Q-amp" which means flow amplification. During a sudden steering change (steering wheel speed greater than 10 rpm), additional steering pump oil flow will bypass the gerotor pump in the HMU and flow directly to the steering cylinders. Steering oil flow to the cylinders is equal to the gerotor pump oil flow plus the bypass oil flow from the steering pump. The steering oil flow is amplified up to 1.6 to 1. The purpose of the flow amplification is to provide quick steering response when sudden steering changes are needed.

2. Load sensing signal line

Load sensing signal pressure flows through a tube (2) to the load sensing controller on the primary steering pump (see Slide No. 137) and the load sensing controller on the secondary steering pump (next slide).

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• HMU tubes

On the front of the HMU are four tubes: - Top left tube: Return to tank - Top right tube: Left turn - Bottom left tube: Pump supply - Bottom right tube: Right turn

• HMU crossover relief valves

Two crossover relief valves are installed in the top of the HMU. The crossover relief valves are installed in series with the left and right turn ports. If an outside force is applied to the front wheels while the steering wheel is stationary, the crossover relief valves provide circuit protection for the steering lines between the steering cylinders and the HMU. The crossover relief valves allow oil to transfer from one end of the steering cylinders to the opposite end of the cylinders. The setting of the crossover relief valves is approximately 27200 ± 690 kPa (3950 ± 100 psi).

• Right crossover relief valve pressure test

To test the right crossover relief valve, install two tees with pressure taps in the right turn steering hose at the steering cylinders. Steer the truck completely to the right against the stops, and shut off the engine. An external pump supply must be connected to one of the pressure taps on the right turn hose. Connect a pressure gauge to the other pressure tap on the right turn hose. Pressurize the steering system, and the reading on the gauge will be the setting of the right crossover relief valve.

• Left crossover relief valve pressure test

To test the left crossover relief valve, install two tees with pressure taps in the left turn steering hose at the steering cylinders. Steer the truck completely to the left against the stops, and shut off the engine. An external pump supply must be connected to one of the pressure taps on the left turn hose. Connect a pressure gauge to the other pressure tap on the left turn hose. Pressurize the steering system, and the reading on the gauge will be the setting of the left crossover relief valve.

• Earlier trucks have external crossover relief valves

On earlier 777D trucks, a separate crossover relief valve block is located on the frame in the engine compartment.

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• 777D Update trucks use dynamic load sensing

All other "D" Series Update trucks use a static load sensing steering system. In a static system, there is load sensing pressure between the HMU and the steering pumps, but no flow. The 777D Update trucks use a dynamic load sensing steering system. In a dynamic system, there is load sensing pressure and flow between the HMU and the steering pumps.

1. Load sensing pilot signal resolver valve

A load sensing pilot signal resolver valve (1) is located on the secondary steering pump load sensing valve. The resolver valve allows load sensing signal oil to flow between the HMU and the primary steering pump or the secondary steering pump. In the NO STEER position, oil flows to the HMU. In a LEFT or RIGHT STEER position, oil flows from the HMU through the signal hose (2).

2. Load sensing signal hose to HMU

3. Load sensing signal hose from primary steering pump

Normally, the secondary steering pump is OFF and the resolver is closed from the HMU to the secondary steering pump. The flow through the hose (3) from the primary steering pump holds the resolver open and load sensing pilot signal pressure is present between the HMU and the piston pump flow compensator.

• "thermal bleed" prevents HMU sticking

The load sensing signal flow from the primary steering pump is also used for "thermal bleed" through the HMU. The "thermal bleed" is used to keep the HMU temperature the same as the rest of the steering system. Keeping the HMU the same temperature prevents sticking.

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STEERING HYDRAULIC SYSTEM

L

STEERING TANK

T LS

CASE DRAIN FILTER

P R

STEERING FILTER

HMU

STEERING PUMP LOAD SENSING VALVE

PRESSURE REDUCING VALVE STEERING PRESSURE SWITCH

LOAD SENSING RESOLVER VALVE

PRIMARY STEERING BACK-UP RELIEF VALVE

SECONDARY STEERING PUMP

SECONDARY STEERING BACK-UP RELIEF VALVE

STEERING VALVE (REAR VIEW) SECONDARY CHECK VALVE

STEERING VALVE (FRONT VIEW)

PRIMARY CHECK VALVE

144 • Steering hydraulic system

Shown is the steering hydraulic system. The primary steering pump pulls supply oil from the steering tank. All piston-type pumps produce a small amount of leakage to the case drain circuit for lubrication and cooling. The case drain oil flows to the steering tank through a case drain filter.

• Steering pressure switch

Steering oil flows from the pump to the steering valve located on the frame behind the right front suspension cylinder. A steering pressure switch monitors the output of the steering pump. The steering pressure switch cannot tolerate high steering system pressures. A pressure reducing valve lowers the steering system pressure to the steering pressure switch.

• Pressure reducing valve

• Secondary steering

If the steering pressure switch signals the Transmission/Chassis ECM that the steering system pressure is low, the ECM will turn ON the secondary steering motor. Secondary steering supply oil flows to the steering valve.

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• Secondary steering load sensing

When the Transmission/Chassis ECM energizes the secondary steering motor, load sensing signal oil will flow from the secondary steering load sensing valve through the load sensing resolver to the HMU. The load sensing valve uses the load sensing signal pressure to control the amount of flow from the secondary steering pump to the steering valve.

• Secondary steering back-up relief valve

Two relief valves are installed in the steering valve. The secondary steering back-up relief valve protects the secondary steering system if the relief valve on the secondary steering pump malfunctions.

• Primary steering back-up relief valve

The primary steering back-up relief valve protects the primary steering system if the high pressure cutoff valve on the steering pump malfunctions.

• Primary and secondary steering check valves

Two check valves are located on the steering valve. The check valves are used to separate the primary and secondary steering systems.

• HMU

The HMU has five ports: - Tank (T) - Pump supply (P) - Load sensing (LS)

- Left turn (L) - Right turn (R)

The Hand Metering Unit (HMU) is located at the base of the steering column behind a cover at the front of the cab. The HMU is connected to the steering wheel and controlled by the operator. Steering supply oil flows to the HMU (P) from the steering valve. Return oil from the HMU (T) flows through the steering valve and the steering filter to the steering tank. The HMU meters the amount of oil sent to the steering cylinders (L and R) by the speed at which the steering wheel is turned. The faster the HMU is turned, the higher the flow sent to the steering cylinders, and the faster the wheels will change direction. • Load sensing pilot signal resolver valve

A load sensing pilot signal resolver valve is located on the secondary steering pump load sensing valve. The resolver valve allows load sensing signal oil to flow between the HMU and the primary steering pump or the secondary steering pump. In the NO STEER position, oil flows to the HMU. In a LEFT or RIGHT STEER position, oil flows from the HMU. Normally, the secondary steering pump is OFF and the resolver is closed from the HMU to the secondary steering pump. The flow from the primary steering pump holds the resolver open and load sensing pilot signal pressure is present between the HMU and the flow compensator on the piston pump.

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STEERING HYDRAULIC SYSTEM

TO STEERING TO LOAD SENSING VALVE RESOLVER

CROSSOVER RELIEF VALVES

PISTON PUMP AND LOAD SENSING CONTROLLER HMU

LOAD SENSING RESOLVER

PRESSURE REDUCING VALVE STEERING PRESSURE SWITCH

LOAD SENSING VALVE DETAIL A

STEERING VALVE PRIMARY STEERING BACK-UP RELIEF VALVE STEERING FILTER

M TRANSMISSION CHASSIS ECM

SEE DETAIL A

SECONDARY STEERING BACK-UP RELIEF VALVE

SECONDARY STEERING PRIMARY RELIEF VALVE

SECONDARY STEERING PUMP

CASE DRAIN FILTER

145 • Steering hydraulic system schematic

Shown is a schematic of the steering hydraulic system used in the 777D Update trucks while in the HOLD position. All the internal valve components and the direction of oil flow can be seen. The primary steering pump pulls supply oil from the steering tank. All piston-type pumps produce a small amount of leakage to the case drain circuit for lubrication and cooling. The case drain oil flows to the steering tank through a case drain filter.

• Steering pressure switch • Pressure reducing valve

Steering oil flows from the pump to the steering valve located on the frame behind the right front suspension cylinder. A steering pressure switch monitors the output of the steering pump. The steering pressure switch cannot tolerate high steering system pressures. A pressure reducing valve lowers the steering system pressure to the steering pressure switch.

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• Secondary steering

If the steering pressure switch signals the Transmission/Chassis ECM that the steering system pressure is low, the ECM will turn ON the secondary steering motor. Secondary steering supply oil flows to the steering valve.

• Secondary steering load sensing

When the Transmission/Chassis ECM energizes the secondary steering motor, load sensing signal oil will flow from the secondary steering load sensing valve through the load sensing resolver to the HMU. The load sensing valve uses the load sensing signal pressure to control the amount of flow from the secondary steering pump to the steering valve.

• Secondary steering back-up relief valve

Two relief valves are installed in the steering valve. The secondary steering back-up relief valve protects the secondary steering system if the relief valve on the secondary steering pump malfunctions.

• Primary steering back-up relief valve

The primary steering back-up relief valve protects the primary steering system if the high pressure cutoff valve on the steering pump malfunctions.

• Primary and secondary steering check valves

Two check valves are located on the steering valve. The check valves are used to separate the primary and secondary steering systems.

• HMU

The Hand Metering Unit (HMU) is located at the base of the steering column behind a cover at the front of the cab. The HMU is connected to the steering wheel and controlled by the operator. Steering supply oil flows to the HMU from the steering valve. Return oil from the HMU flows through the steering valve and the steering filter to the steering tank. The HMU meters the amount of oil sent to the steering cylinders by the speed at which the steering wheel is turned. The faster the HMU is turned, the higher the flow sent to the steering cylinders, and the faster the wheels will change direction.

• Load sensing pilot signal resolver valve

A load sensing pilot signal resolver valve is located on the secondary steering pump load sensing valve. The resolver valve allows load sensing signal oil to flow between the HMU and the primary steering pump or the secondary steering pump. In the NO STEER position, oil flows to the HMU. In a LEFT or RIGHT STEER position, oil flows from the HMU.

• HMU crossover relief valves

Two crossover relief valves are installed in the top of the HMU. The crossover relief valves are installed in series with the left and right turn ports. If an outside force is applied to the front wheels while the steering wheel is stationary, the crossover relief valves provide circuit protection for the steering lines between the steering cylinders and the HMU. The crossover relief valves allow oil to transfer from one end of the steering cylinders to the opposite end of the cylinders.

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146

HOIST SYSTEM • Hoist system controlled by Transmission/Chassis ECM

The hoist system on the 777D Update trucks is electronically controlled by the Transmission/Chassis ECM.

• Hoist SNUB control

The hoist valve has a fifth position referred to as the SNUB position. The operator is unaware of the SNUB position because a corresponding lever position is not provided. When the body is being lowered, just before the body contacts the frame, the Transmission/Chassis ECM signals the hoist lower solenoid to move the hoist valve spool to the SNUB position. In the SNUB position, the body float speed is reduced to prevent the body from making hard contact with the frame.

• Hoist system must be enabled with ET

The hoist system can be enabled or disabled using ET. All trucks shipped from the factory without bodies installed are set at the Hoist Enable Status 2. The Hoist Enable Status 2 is a test mode only and will prevent the hoist cylinders from accidentally being activated. After the body is installed, change the Hoist Enable Status to 1 for the hoist system to function properly.

The hoist control system operates similarly to the earlier 777D trucks. The four hoist lever positions are: RAISE, HOLD, FLOAT and LOWER.

NOTE: The hoist system can be enabled or disabled using ET. If the hoist system fails to function, check the hoist status configuration in the Transmission/Chassis ECM.

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• Hoist lever (arrow)

The operator controls the hoist lever (arrow). The four positions of the hoist lever are RAISE, HOLD, FLOAT and LOWER.

• Hoist lever normally in FLOAT position

The truck should normally be operated with the hoist lever in the FLOAT position. Traveling with the hoist in the FLOAT position will make sure the weight of the body is on the frame and body pads and not on the hoist cylinders. The hoist control valve will actually be in the SNUB position.

• Reverse inhibitor operation

If the transmission is in REVERSE when the body is being raised, the hoist lever sensor is used to shift the transmission to NEUTRAL. The transmission will remain in NEUTRAL until: 1. The hoist lever is moved into the HOLD or FLOAT position; and 2. the shift lever has been cycled into and out of NEUTRAL. NOTE: If the truck is started with the body raised and the hoist lever in FLOAT, the lever must be moved into HOLD and then FLOAT before the body will lower.

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148 • Hoist control position sensor (arrow) • Sensor energizes two solenoids on hoist valve • Hoist lever sensor provides modulation • Sensor performs three functions: - Raises and lowers body - Neutralizes transmission in REVERSE - Starts a new TPMS cycle • Hoist lever sensor diagnostics - Supply voltage

- Signal Duty Cycle

The hoist lever controls a Pulse Width Modulated (PWM) position sensor (arrow). The PWM sensor sends duty cycle input signals to the Transmission/Chassis ECM. Depending on the position of the sensor and the corresponding duty cycle, one of the two solenoids located on the hoist valve is energized. The four positions of the hoist lever are RAISE, HOLD, FLOAT and LOWER, but since the sensor provides a duty cycle signal that changes for all positions of the hoist lever, the operator can modulate the speed of the hoist cylinders. The hoist lever sensor also replaces the body raise switch (transmission neutralizer switch) that was located behind the operator's seat. The hoist lever sensor performs three functions: - Raises and lowers the body - Neutralizes the transmission in REVERSE - Starts a new TPMS cycle The hoist lever position sensor receives 24 Volts from the Transmission/ Chassis ECM. To check the supply voltage of the sensor, connect a multimeter between Pins A and B of the sensor connector. Set the meter to read "DC Volts." To check the output signal of the hoist lever position sensor, connect a multimeter between Pins B and C of the hoist lever position sensor connector. Set the meter to read "Duty Cycle." The duty cycle output of the sensor should be approximately 5 to 95% between full RAISE to full LOWER.

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• Hoist, converter and brake hydraulic tank 1. Oil level sight gauge door

Shown is the hoist, converter and brake hydraulic tank. The oil level is checked by opening the small door (1) and looking through the sight gauge. The oil level should first be checked with cold oil and the engine stopped. The level should again be checked with warm oil and the engine running.

2. Lower sight gauge for oil level with raised cylinders

The lower sight gauge (2) can be used to fill the tank when the hoist cylinders are in the RAISED position. When the hoist cylinders are lowered, the hydraulic oil level will increase. After the hoist cylinders are lowered, check the hydraulic tank oil level with the upper sight gauge as explained above.

• Use only TDTO oil

Use only Transmission Drive Train Oil (TDTO) with a specification of TO-4 or newer. TDTO TO-4 oil: - Provides maximum frictional capability required for the clutch discs used in the brakes. - Increases brake holding capability by reducing brake slippage. - Controls brake chatter.

3. Breather

Check the hoist and brake hydraulic tank breather (3) for restriction. Clean the filter if it is restricted.

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150

• Rear of hoist, converter and brake oil tank 1. Hoist pump suction screen 2. Hoist oil return port 3. Brake cooling oil return ports • Other hydraulic tank ports: 4. Transmission charging pump suction 5. Transmission return 6. Torque converter pump suction 7. Attachment brake cooling pump suction 8. Torque converter inlet relief valve return port

Shown is the rear of the hoist, converter and brake hydraulic tank. The hoist pump pulls oil from the tank through the suction screen (1) located in the rear of the tank. Oil returns from the hoist valve through the port (2). Brake cooling oil returns to the hydraulic tank through the three upper ports (3). Other ports located on the hydraulic tank are: - Transmission charging pump suction (4) - Transmission return (5) - Torque converter pump suction (6) - Attachment brake cooling pump suction (7) - Torque converter inlet relief valve return port (8)

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1

2

151

1. Hoist pump 2. Hoist system pressure tap

The hoist pump (1) is located at the top rear of the pump drive. Oil flows from the hoist pump to the hoist control valve. The hoist system pressure can be tested at the pressure tap (2). The hoist system relief pressures are different in the RAISE and LOWER positions.

• Hoist pressure during RAISE

The hoist system relief pressure during RAISE is: 18950 + 520 - 0 kPa (2750 + 75 - 0 psi)

• Hoist pressure during LOWER

The hoist system relief pressure during LOWER is: 3450 ± 350 kPa (500 ± 50 psi)

• Body up switch must be in RAISE to check LOWER relief

The body up switch (see Slide No. 132) must be in the RAISE position before the LOWER relief valve setting can be tested. Move a magnet past the body up switch until the body up alert indicator on the dash turns ON. If the body up switch is in the LOWER position, the Transmission/ Chassis ECM will hold the hoist valve in the SNUB position and the LOWER relief valve will not open.

• Hoist pressures during HOLD, FLOAT and SNUB

In the HOLD, FLOAT and SNUB positions, the gauge will show the brake cooling system pressure, which is a result of the restriction in the coolers, brakes and hoses (normally much lower than the actual oil cooler relief valve setting). The maximum pressure is limited by the oil cooler relief valve, which has a setting of 586 ± 14 kPa (85 ± 2 psi).

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3 2

4

1

5

6

152

• Hoist control valve • Brake release oil used for hoist pilot

1. RAISE position solenoid valve 2. LOWER position solenoid valve

Oil flows from the hoist pump to the hoist control valve located on the frame cross-tube between the hoist cylinder lower mounts. The hoist valve uses brake release oil as the pilot oil to shift the directional spool inside the hoist valve. Brake release oil enters the hydraulic actuators on both ends of the hoist valve through the small hoses. The brake release (hoist pilot) oil pressure is 4700 ± 200 kPa (680 ± 30 psi) Pilot oil pressure is always present at both ends of the directional spool. Two solenoid valves are used to drain the pilot oil from the ends of the directional spool, which then allows the spool to move. The solenoid on the right is the RAISE solenoid valve (1), and the solenoid on the left is the LOWER solenoid valve (2).

• Hoist solenoids "dither" when not in the HOLD position

The RAISE and LOWER solenoid valves constantly receive approximately 300 millivolts at a frequency of 80 Hz when they are in any position except HOLD. The excitation, referred to as "dither," is used to keep the solenoids in a ready state for quick response.

• Hoist solenoids receive between 0 and 1.9 amps

When the Transmission/Chassis ECM receives an input signal from the hoist lever sensor, the ECM sends an output signal current between 0 and 1.9 amps to one of the solenoids. The amount of current sent to the solenoid determines how much pilot oil is drained from the end of the directional spool and, therefore, how far the directional spool travels toward the solenoid.

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3. Tube to oil cooler and brakes

When the hoist control valve is in the HOLD, FLOAT or SNUB position, all the hoist pump oil flows through the large tube (3) and the brake oil cooler located behind the engine (see Slide No. 78) to the brakes (see Slides No. 108 and 109).

4. Oil cooler relief valve plug

An oil cooler relief valve is located in the hoist control valve behind the large plug (4). The relief valve limits the brake oil cooling pressure when the hoist valve is in the HOLD, FLOAT or SNUB position. The setting of the oil cooler relief valve is 586 ± 14 kPa (85 ± 2 psi).

5. Hoist cylinder head end--RAISE pressure tap

The two hoist system pressure taps are located in junction blocks between the two hoist cylinders. The left tap (5) is used to test the RAISE hoist pressure. The right tap (6) is used to test the LOWER hoist pressure. The relief valve pressure setting is tested with the engine at HIGH IDLE and the hoist valve in the RAISE or LOWER position.

6. Hoist cylinder rod end--LOWER pressure tap • Body up switch must be in RAISE to check LOWER relief

The body up switch (see Slide No. 132) must be in the RAISE position before the LOWER relief valve setting can be tested. Move a magnet past the body up switch until the body up alert indicator on the dash turns ON. If the body up switch is in the LOWER position, the Transmission/ Chassis ECM will hold the hoist valve in the SNUB position and the LOWER relief valve will not open.

• Orifice plate

An orifice plate is installed between the upper hose and the rod end port on both hoist cylinders. The orifice plate restricts the flow of oil from the rod end of the hoist cylinders. The orifice plate prevents cavitation of the cylinders when the body raises faster than the pump can supply oil to the cylinders (caused by a sudden shift of the load).

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1. Load check valve plug

Shown is the right side of the hoist valve. The load check valve is located behind the plug (1). When the directional spool is initially shifted, the load check valve remains closed until the supply pressure is higher than the pressure in the hoist cylinders. The load check valve prevents the body from dropping before the RAISE pressure increases.

2. Hoist pilot supply port

Hoist pilot supply oil (brake release) enters the hydraulic actuators through the port (2). When in HOLD, pilot oil pressure is present at both ends of the directional spool. When a solenoid is energized, pilot oil is drained from the end of the directional spool, which then allows the spool to move. The drain port is located behind the plug (3). The control pressure, which holds the spool in the appropriate position, can be measured at the port (4).

3. Hoist pilot drain port 4. Hoist pilot control port

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154

The hoist system relief pressures are controlled by the two relief valves located on top of the hoist valve. 1. RAISE relief valve

The RAISE relief valve (1) limits the pressure in the hoist system during RAISE. The hoist system relief pressure during RAISE is 18950 + 520 - 0 kPa (2750 + 75 - 0 psi)

2. LOWER relief valve

The LOWER relief valve (2) limits the pressure in the hoist system during LOWER. The hoist system relief pressure during LOWER is 3450 ± 350 kPa (500 ± 50 psi).

3. Dual stage relief valve signal spool plug

The dual stage relief valve signal spool is located behind the plug (3). When the hoist valve is in the RAISE position, the directional spool sends hoist cylinder raise pressure to the dual stage relief valve signal spool. The dual stage relief valve signal spool moves and blocks the supply pressure from opening the low pressure relief valve.

• Hoist system must be adjusted with ET

NOTE: The hoist valve LOWER position is an adjustable parameter in the Transmission/Chassis ECM using ET. The slight adjustment provides a means to compensate for valve differences. The adjustment range is from -5 to +5 with zero as the default. A negative number will decrease the lower speed and a positive number will increase the lower speed. With the engine at HIGH IDLE and the hoist lever in FLOAT, pump output pressure must be less than 1725 kPa (250 psi). The hoist lever must be in HOLD when changing the setting.

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RAISE SOLENOID

BRAKE COOLING RELIEF VALVE

PARKING BRAKE RELEASE PRESSURE

LOW PRESSURE RELIEF VALVE

MAIN RELIEF DUMP VALVE TO BRAKE COOLING

HIGH PRESSURE RELIEF VALVE

TO HOIST CYLINDER ROD END

DUAL STAGE RELIEF VALVE SIGNAL STEM

TO HOIST CYLINDER HEAD END

LOAD CHECK VALVE

HOIST CONTROL VALVE HOLD PARKING BRAKE RELEASE PRESSURE LOWER SOLENOID

155 • Hoist valve in HOLD

• Hoist supply oil flows to brake cooling

Shown is a sectional view of the hoist control valve in the HOLD position. Pilot oil pressure is present at both ends of the directional spool. The spool is held in the centered position by the centering springs and the pilot oil. Passages in the directional spool vent the dual stage relief valve signal stem to the tank. All the hoist pump oil flows through the brake oil cooler to the rear brakes. The position of the directional spool blocks the oil in the head and rod end of the hoist cylinders.

• Brake cooling pressure measured at pump in HOLD

A gauge connected to a pressure tap at the pump while the hoist valve is in the HOLD position will show the brake cooling system pressure, which is a result of the restriction in the coolers, brakes and hoses. The maximum pressure in the circuit should correspond to the setting of the front brake oil cooler relief valve. The setting of the oil cooler relief valve is 586 ± 14 kPa (85 ± 2 psi).

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ON RAISE SOLENOID

BRAKE COOLING RELIEF VALVE

PARKING BRAKE RELEASE PRESSURE

LOW PRESSURE RELIEF VALVE

MAIN RELIEF DUMP VALVE TO BRAKE COOLING

HIGH PRESSURE RELIEF VALVE

FROM HOIST CYLINDER ROD END

DUAL STAGE RELIEF VALVE SIGNAL STEM

TO HOIST CYLINDER HEAD END

LOAD CHECK VALVE

HOIST CONTROL VALVE RAISE PARKING BRAKE RELEASE PRESSURE LOWER SOLENOID

156 • Hoist valve in RAISE

Shown is a sectional view of the hoist control valve in the RAISE position. The raise solenoid is ENERGIZED and drains pilot oil from the upper end of the directional spool. The directional spool moves up. Pump oil flows past the load check valve and the directional spool to the head end of the hoist cylinders.

• Load check valve operation

When the directional spool is initially shifted, the load check valve remains closed until the supply pressure is higher than the pressure in the hoist cylinders. The load check valve prevents the body from dropping before the RAISE pressure increases.

• Dual stage relief signal stem operation

The directional spool also sends hoist cylinder raise pressure to the dual stage relief valve signal stem. The dual stage relief valve signal stem moves down and blocks the supply pressure from opening the low pressure relief valve. Oil flowing from the rod end of the hoist cylinders flows freely through the brake oil cooler to the brakes.

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• High pressure relief setting checked during RAISE at HIGH IDLE

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If the pressure in the head end of the hoist cylinders exceeds the relief valve settings, the high pressure relief valve will open. When the high pressure relief valve opens, the dump valve moves to the left and pump oil flows to the tank. The high pressure hoist relief valve setting is checked at the hoist pump pressure tap or the head end pressure tap located on a junction block between the two hoist cylinders. Check the relief pressure with the hoist lever in the RAISE position and the engine at HIGH IDLE.

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RAISE SOLENOID

BRAKE COOLING RELIEF VALVE

PARKING BRAKE RELEASE PRESSURE

LOW PRESSURE RELIEF VALVE

MAIN RELIEF DUMP VALVE TO BRAKE COOLING

HIGH PRESSURE RELIEF VALVE

TO HOIST CYLINDER ROD END

DUAL STAGE RELIEF VALVE SIGNAL STEM

FROM HOIST CYLINDER HEAD END

LOAD CHECK VALVE

HOIST CONTROL VALVE LOWER/POWER DOWN PARKING BRAKE RELEASE PRESSURE LOWER SOLENOID

ON

157 • Hoist valve in LOWER (power down)

Shown is a sectional view of the hoist control valve in the LOWER (power down) position. The LOWER solenoid is energized and drains pilot oil from the lower end of the directional spool. The directional spool moves down. Supply oil from the pump flows past the load check valve and the directional spool to the rod end of the hoist cylinders. Oil in the head end of the hoist cylinders flows to the tank through 15 holes in the directional spool. The supply oil in the rod end of the cylinders and the weight of the body move the cylinders to their retracted positions.

• Body up switch controls SNUB position

Just before the body contacts the frame, the body up switch sends a signal to the Transmission/Chassis ECM to move the directional spool to the SNUB position. In the SNUB position, the directional spool moves slightly to restrict the flow of head end oil through only FIVE holes in the spool and lower the body gradually.

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• Dual stage relief signal stem operation

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The directional spool also vents the passage to the dual stage relief valve signal stem. The dual stage relief valve signal stem allows supply pressure to be limited by the low pressure relief valve. If the pressure in the rod end of the hoist cylinders exceeds 3450 ± 350 kPa (500 ± 50 psi), the low pressure relief valve will open. When the low pressure relief valve opens, the dump valve moves to the left and pump oil flows to the tank.

• Low pressure relief setting checked during LOWER at HIGH IDLE

The low pressure hoist relief valve setting is checked at the rod end pressure tap located on a junction block between the two hoist cylinders. Check the relief pressures with the hoist lever in the LOWER position and the engine at HIGH IDLE.

• Body up switch must be in RAISE to check LOWER relief

The body up switch must be in the RAISE position before the LOWER relief valve setting can be tested. Move a magnet past the body up switch until the body up alert indicator on the dash turns ON. If the body up switch is in the LOWER position, the Transmission/Chassis ECM will hold the hoist valve in the SNUB position, and the LOWER relief valve will not open.

• Hoist system must be adjusted with ET

NOTE: The hoist valve LOWER position is an adjustable parameter in the Transmission/Chassis ECM using ET. The slight adjustment provides a means to compensate for valve differences. The adjustment range is from -5 to +5 with zero as the default. A negative number will decrease the lower speed and a positive number will increase the lower speed. With the engine at HIGH IDLE and the hoist lever in FLOAT, pump output pressure must be less than 1725 kPa (250 psi). The hoist lever must be in HOLD when changing the setting.

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RAISE SOLENOID

BRAKE COOLING RELIEF VALVE

PARKING BRAKE RELEASE PRESSURE

LOW PRESSURE RELIEF VALVE

MAIN RELIEF DUMP VALVE TO BRAKE COOLING

HIGH PRESSURE RELIEF VALVE

TO HOIST CYLINDER ROD END

DUAL STAGE RELIEF VALVE SIGNAL STEM

FROM HOIST CYLINDER HEAD END

LOAD CHECK VALVE

HOIST CONTROL VALVE FLOAT PARKING BRAKE RELEASE PRESSURE LOWER SOLENOID

ON

158 • Hoist valve in FLOAT

Shown is a sectional view of the hoist valve in the FLOAT position. The LOWER solenoid is partially energized and drains some of the pilot oil at the lower end of the directional spool to the tank. The directional spool moves down. Because the pilot oil is only partially drained, the directional spool does not move down as far as during LOWER. Pump supply oil flows past the load check valve and the directional spool to the rod end of the hoist cylinders. Oil in the head end of the hoist cylinders flows to the tank. The position of the directional spool permits the pressure of the oil flowing to the brake oil cooler to be felt at the rod end of the hoist cylinders.

• Operate truck with hoist lever in FLOAT

The truck should normally be operated with the hoist lever in the FLOAT position. Traveling with the hoist in the FLOAT position will make sure the weight of the body is on the frame and body pads and not on the hoist cylinders. The hoist valve will actually be in the SNUB position.

• Valve moves to SNUB position

Just before the body contacts the frame, the body up switch sends a signal to the Transmission/Chassis ECM to move the directional spool to the SNUB position. In the SNUB position, the valve spool moves slightly to restrict the flow of oil and lower the body gradually.

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RAISE SOLENOID PARKING BRAKE RELEASE PRESSURE

LOW PRESSURE RELIEF VALVE

BRAKE COOLING RELIEF VALVE

MAIN RELIEF DUMP VALVE TO BRAKE COOLING

HIGH PRESSURE RELIEF VALVE

TO HOIST CYLINDER ROD END

DUAL STAGE RELIEF VALVE SIGNAL STEM

FROM HOIST CYLINDER HEAD END

LOAD CHECK VALVE

HOIST CONTROL VALVE SNUB PARKING BRAKE RELEASE PRESSURE LOWER SOLENOID

ON

159 • Hoist valve in SNUB

Shown is a sectional view of the hoist control valve in the SNUB position. As the body is lowered, just before the body contacts the frame, the body up switch sends a signal to the Transmission/Chassis ECM to move the directional spool to the SNUB position. In the SNUB position, the directional spool moves slightly to a position between HOLD and FLOAT. The SNUB position restricts the flow of oil and lowers the body gradually.

• Hoist system always in SNUB when body is down

The operator does not control the SNUB position. When the hoist lever is in the LOWER or FLOAT position and the body up switch is in the DOWN position, the hoist control valve is in the SNUB position.

• Brake cooling pressure

A gauge connected to the rod end pressure tap while the hoist control valve is in the SNUB position will show the brake cooling system pressure, which is a result of the restriction in the coolers, brakes and hoses. Brake cooling system pressure will be approximately 172 kPa (25 psi) at HIGH IDLE. The maximum pressure in the circuit should correspond to the setting of the brake oil cooler relief valve. The setting of the oil cooler relief valve is 586 ± 14 kPa (85 ± 2 psi).

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160

• Two-stage hoist cylinders

Shown are the two-stage hoist cylinders used to raise the body. Oil flows from the hoist control valve to the two hoist cylinders when the directional spool in the hoist control valve is not in HOLD.

• Body pads (arrow)

Check the condition of the body pads (arrow) for wear or damage.

• Lower body with dead engine

Hoist pilot pressure is required to lower the body with a dead engine. The towing pump can be used to provide the hoist pilot oil. To lower the body with a dead engine: - Move the diverter (towing) valve to the towing position (see Slides No. 187 and 188). - Turn ON the key start switch so the towing motor and the hoist solenoids can be energized. - Move the hoist lever to the RAISE position for 15 seconds, then to the FLOAT position. - Depress the secondary steering and brake release switch on the dash (see Slide No. 46).

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HOIST HYDRAULIC SYSTEM (TOP VIEW)

HOIST PUMP

REAR BRAKES

DIVERTER VALVE

BRAKE OIL COOLER (BEHIND ENGINE)

HOIST VALVE (SIDE VIEW)

HOIST CYLINDERS

HOIST, CONVERTER AND BRAKE OIL COOLER

PARKING BRAKE RELEASE VALVE

TOW VALVE

M

PARKING BRAKE FILTER

TOWING PUMP

161 • Hoist hydraulic system

The hoist pump pulls oil from the hydraulic tank through the suction screen located in the rear of the tank. Oil flows from the hoist pump to the hoist valve. The hoist valve uses brake release oil as the pilot oil to shift the directional spool inside the hoist control valve. Oil flows from the brake release valve to both ends of the hoist control valve. The brake release oil pressure is 4700 ± 200 kPa (680 ± 30 psi). Pilot pressure is always present at both ends of the directional spool. Two solenoid valves are used to drain the pilot oil from the ends of the directional spool, which then allows the spool to move.

• Hoist oil flows to oil cooler and brakes

When the hoist control valve is in the HOLD, FLOAT or SNUB position, all the hoist pump oil flows through the brake oil cooler located behind the engine above the torque converter. Oil flows from the oil cooler, through the rear brakes, and returns to the hydraulic tank.

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• Oil cooler relief valve

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An oil cooler relief valve is located in the hoist control valve. The relief valve limits the brake oil cooling pressure when the hoist control valve is in the HOLD, FLOAT or SNUB position. The setting of the oil cooler relief valve is 586 ± 14 kPa (85 ± 2 psi). Oil flows from the hoist control valve to the two hoist cylinders when the directional spool in the hoist control valve is not in HOLD.

• Orifice plate

An orifice plate is installed between the upper hose and the rod end port on both hoist cylinders. The orifice plate prevents cavitation of the cylinders when the body raises faster than the pump can supply oil to the cylinders (caused by a sudden shift of the load).

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HOIST HYDRAULIC SYSTEM

TOWING PUMP

TOWING VALVE

BRAKE RELEASE VALVE

M

BRAKE RELEASE PUMP BRAKE RELEASE FILTER HOIST PUMP

LOWER RELIEF VALVE

DIVERTER VALVE

HYDRAULIC TANK

OIL COOLER AND SCREEN

ORIFICE PLATES

RAISE RELIEF VALVE

HOIST CYLINDERS

REAR BRAKES DUAL STAGE SIGNAL SPOOL BRAKE COOLING RELIEF VALVE LOWER SOLENOID

RAISE SOLENOID

POWER DOWN

FLOAT

RAISE

SNUB HOLD

LOAD CHECK

MAIN RELIEF DUMP SPOOL

162 • Hoist hydraulic system

Shown is a schematic of the hoist hydraulic system used in the 777D Update trucks.

• Directional spool operation

The hoist valve uses brake release oil as the pilot oil to shift the directional spool inside the hoist control valve. Oil flows from the brake release valve to both ends of the hoist control valve. Pilot pressure is always present at both ends of the directional spool. Two solenoid valves are used to drain the pilot oil from the ends of the directional spool, which then allows the centering springs and the pressure on the opposite end of the spool to move the spool. The solenoid on the left is the RAISE solenoid valve and the solenoid on the right is the LOWER solenoid valve. When the RAISE solenoid is energized, the directional spool will move toward the RAISE solenoid.

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• Hoist solenoids "dither" when not in the HOLD position

The RAISE and LOWER solenoid valves constantly receive approximately 300 millivolts at a frequency of 80 Hz when they are in any position except HOLD. The excitation, referred to as "dither," is used to keep the solenoids in a ready state for quick response.

• Hoist lever sensor provides modulation

The hoist lever controls a Pulse Width Modulated (PWM) position sensor. The PWM sensor sends duty cycle input signals to the Transmission/Chassis ECM. Depending on the position of the sensor and the corresponding duty cycle, one of the two solenoids located on the hoist valve is energized.

• Hoist solenoids

The four positions of the hoist lever are RAISE, HOLD, FLOAT and LOWER, but since the sensor provides a duty cycle signal that changes for all positions of the hoist lever, the operator can modulate the speed of the hoist cylinders.

• Hoist lever normally in FLOAT position

When the Transmission/Chassis ECM receives an input signal from the hoist lever sensor, the ECM sends an output signal current between 0 and 1.9 amps to one of the solenoids. The amount of current sent to the solenoid determines how much pilot oil is drained from the end of the directional spool and, therefore, the distance that the directional spool travels.

• Hoist SNUB control

The truck should normally be operated with the hoist lever in the FLOAT position. Traveling with the hoist in the FLOAT position will make sure the weight of the body is on the frame and body pads and not on the hoist cylinders. The hoist valve will actually be in the SNUB position.

• RAISE position

The operator is unaware of the SNUB position because this position has no corresponding lever position. As the body is lowered, just before the body contacts the frame, the body float speed is reduced to prevent the body from making hard contact with the frame.

• LOWER position

When the hoist control valve is in the RAISE position, pump supply oil flows to the head end of the hoist cylinders. Pump supply oil also flows to the dual stage signal spool and moves the spool to the left. When the dual stage signal spool moves to the left, pump supply oil is blocked from the LOWER relief valve, and the RAISE relief valve will limit the hoist system pressure. When the hoist control valve is in the LOWER (POWER DOWN), FLOAT or SNUB position, pump supply oil flows to the rod end of the hoist cylinders. Pump supply oil is blocked from the dual stage signal spool and the spring holds the spool in the right position. When the dual stage signal spool is in the right position, pump supply oil can flow to the LOWER relief valve, and hoist system pressure is controlled by the

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163

AIR SYSTEM AND BRAKES • Two brake systems: - Parking/secondary brake system - Service/retarder brake system

Two separate brake systems are used on the 777D Update trucks. The two brake systems are: the parking/secondary brake system and the service/retarder brake system. The parking/secondary brakes are spring engaged and hydraulically released. The service/retarder brakes are engaged hydraulically by an air-over-oil brake system. The 777D Update trucks are also equipped with an air system. An engine driven air compressor supplies the air and fills three tanks. Air from the tanks provides energy to perform several functions:

• Air system functions

-

Service and retarder brake control Secondary and parking brake control Horn, air seat and cab clean-out Attachment exhaust diverter Attachment air start

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164

• Oil cooled brake assembly • Seals prevent oil leaks or transfer

The rear brakes on the 777D Update trucks are oil cooled. Shown is a cutaway illustration of an oil cooled brake assembly. The brakes are environmentally sealed and adjustment free. Oil continually flows through the brake discs for cooling. Duo-Cone seals prevent the cooling oil from leaking to the ground or transferring into the axle housing. The wheel bearing adjustment must be maintained to keep the Duo-Cone seals from leaking.

• Small piston ENGAGES secondary and parking brakes

The smaller piston (yellow) is used to ENGAGE the secondary and parking brakes. The parking brakes are spring ENGAGED and hydraulically RELEASED.

• Large piston ENGAGES service and retarder brakes

The larger piston (purple) is used to ENGAGE the service and retarder brakes. The service and retarder brakes are engaged hydraulically by an air-over-oil brake system.

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CALIPER DISC BRAKE ENGAGED

PISTON BLEED VALVE CALIPER

CARRIER LINING FROM BRAKE CYLINDER DISC

165 • Front brake components: - Caliper assembly - Disc - Bleed valve

The front brakes used on the 777D Update trucks are the disc and caliper design (see Slide No. 9). The brake caliper assemblies are fastened to the spindle and do not rotate. The brake disc is fastened to the wheel and rotates with the wheel. Air can be bled from the front brakes through the bleed valves. During a brake application, hydraulic oil from the brake cylinders forces the brake pistons against the brake carrier linings (brake pads). The brake linings are forced against the disc to stop the rotation of the wheel.

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BRAKE ACTUATION PRESSURE

777D ATTACHMENT FRONT BRAKE

DISASSEMBLY SERVICE PLUG

166 • Attachment oil cooled front brakes

Shown is a sectional view of the attachment oil cooled front brake assembly for 777D Update Off-highway Trucks. The attachment front brakes are also environmentally sealed and adjustment free. Oil continually flows through the brake discs for cooling.

• Piston ENGAGES the retarder and service brakes

The piston (yellow) is used to ENGAGE the service/retarder brakes. The 777D Update attachment front brakes do not have a second piston for the parking/secondary brakes.

• Attachment front brakes not used for parking/secondary • Install 3/8 inch bolts before disassembly

When the wheel is removed for service, the small plug at the lower left must be removed (the brake assembly is equipped with two similar plugs). Two 3/8 inch bolts must be installed at the plug locations to hold the brake discs and plates in position during wheel removal. If the 3/8 inch bolts are not installed, the discs and plates will slide out of position during disassembly and alignment of the teeth on the discs and plates with the splines on the stationary ring and the wheel during installation will be very difficult.

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2

1

167

Air Charging System • Air compressor

The air system is charged by an air compressor mounted on the front of the engine.

1. Air compressor governor

System pressure is controlled by the governor (1). The governor maintains the system pressure between 660 and 830 kPa (95 and 120 psi).

• Air compressor governor adjustment

The governor setting can be adjusted with a screw below the cover on the governor. Turn the adjustment screw OUT to increase the pressure and IN to decrease the pressure.

2. Supply air pressure regulator

Supply air flows from the aftercooler housing to the air compressor through the pressure regulator (2). The pressure regulator limits the boost supply pressure to 70 kPa (10 psi). Reducing the supply pressure to the air compressor reduces the maximum cylinder pressure that can be generated in the air compressor. Reducing the cylinder pressure reduces the air compressor temperature and therefore increases the air compressor life. Air compressors that receive supply air from the atmosphere do not require a pressure regulator.

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1

3 2

4

168

1. Air dryer

Air flows from the air compressor to the air dryer (1) located behind the left front tire. The air dryer removes contaminants and moisture from the air system. The condition of the desiccant in the air dryer should be checked every 500 hours and changed periodically (determined by the humidity of the local climate).

2. Purge valve signal hose

When the air compressor governor senses that system air pressure is at the cut-out pressure of 830 kPa (120 psi), the governor sends an air pressure signal to the purge valve through the hose (2). The purge valve opens and air pressure that is trapped in the air dryer is exhausted through the desiccant, an oil filter and the purge valve.

3. Air system relief valve

An air system relief valve (3) is located on the air dryer to protect the system if the air compressor governor malfunctions. The setting of the relief valve is 1380 kPa (200 psi).

4. Heating element

A heating element (4) prevents moisture in the dryer from freezing in cold weather.

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169

1. Service/retarder brake tanks

Air flows through the air dryer and fills three tanks. The two service/retarder brake tanks (1) are located on the hydraulic tank.

• Check valve

A check valve prevents a loss of air if an air line breaks upstream of the air tanks.

2. Relief valve

A relief valve (2) is installed in the service/retarder brake tanks. This relief valve protects the air system when the air dryer has exhausted and the ball check valve in the air dryer outlet port closes, which separates the air system from the air dryer relief valve. The setting of the relief valve is 1034 ± 55 kPa (150 ± 8 psi). A third tank is located behind the cab and supplies air for the parking and secondary brake system (see Slide No. 171).

3. Drain condensation

Condensation should be drained from the tanks daily through the drain valve (3).

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4 1

2

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170

1. Pressure protection valve

Located behind the operator’s station is a pressure protection valve (1). Supply air flows from the service and retarder brake tanks, through the pressure protection valve, to the secondary air system and accessories. The pressure protection valve opens at 550 kPa (80 psi) and closes at 482 kPa (70 psi). If the secondary air lines or an accessory circuit fails, the pressure protection valve maintains a minimum of 482 kPa (70 psi) in the service and retarder brake circuit.

• Pressure protection valve test

To test the pressure protection valve, drain the air pressure to approximately 345 kPa (50 psi). Set the monitoring system to show the system air pressure gauge. With the engine running at LOW IDLE, press the horn button. Record the air pressure when the horn sounds. This pressure reading is the OPEN setting of the pressure protection valve. Slowly drain the air pressure and record the air pressure when the horn turns off. This pressure reading is the setting of the pressure protection valve when it CLOSES.

2. Air system pressure sensor

The air system pressure sensor (2) provides an input signal to the Caterpillar Monitoring System, which informs the operator if the air system pressure is low.

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3. Parking/ secondary brake pressure switch

The parking and secondary brake pressure switch (3) provides an input signal to the Transmission/Chassis ECM. The Transmission/Chassis ECM uses the signal to override the anti-hunt timer for rapid downshifting. The ECM also provides the signal to the Caterpillar Monitoring System, which informs the operator if the parking or secondary brake is ENGAGED.

4. Front brake ratio valve

The front brake ratio valve (4) controls the air pressure to the front brakes when the front brake ON/OFF valve (see slide No. 35) is in the ON position (used only on trucks with caliper disc front brakes).

- Only on trucks with caliper disc front brakes

When the service brake pedal is PARTIALLY DEPRESSED and the outlet pressure is below 420 kPa (60 psi), only 50% of the supply air pressure is allowed through the ratio valve to the front brakes. When the outlet pressure from the service brake valve is above 420 kPa (60 psi), 100% of the supply air pressure is allowed to flow to the front brakes. Restricting the air flow to the front brakes during PARTIAL ENGAGEMENT allows the rear brakes to engage first and provides more control to the operator. During FULL ENGAGEMENT, the operator will receive the maximum braking capacity.

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3

2

171

1. Parking/secondary brake tank

Located behind the operator’s station is the parking and secondary brake air tank (1). A drain valve is located near the engine oil dipstick. Moisture should be drained from the tank daily through the drain valve (see Slide No. 30).

• Check valve

A check valve prevents a loss of air if an air line breaks upstream of the tank.

2. Stoplight switch

The stoplight switch (2) and the transmission service/retarder switch (3) are activated when the service brakes, the manual retarder or the Automatic Retarder Control (ARC) is ENGAGED.

3. Transmission service/retarder switch

The transmission service/retarder brake pressure switch provides an input signal to the Transmission/Chassis ECM. The Transmission/Chassis ECM uses the signal to raise the transmission shift points and to override the anti-hunt timer for rapid downshifting. • Service/retarder switch used as TCS input

The Traction Control System (TCS) also uses the service/retarder brake switch input signal through the CAT Data Link (see Slide No. 201).

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AIR CHARGING SYSTEM

AIR COMPRESSOR AND GOVERNOR

RELIEF VALVE

ONE WAY CHECK VALVE

AIR DRYER

AIR TANK (SERVICE)

AIR TANK (SERVICE) CAB ENCLOSURE

AIR PRESSURE SENSOR

DRAIN VALVE

PRESSURE PROTECTION VALVE TO AIR SEAT

HORN RELAY

PARKING/ SECONDARY TANK

TO BRAKE COOLER COLD OIL VALVE, BRAKE RELAYS, RETARDER VALVE AND SERVICE BRAKE PEDAL

AIR HORN

172 • Air charging system schematic

This schematic shows the flow of air through the air charging system. Air flows from the air compressor, through the air dryer, to the service and retarder brake tanks. Air from the service and retarder brake tanks enters the pressure protection valve. When the pressure in the service and retarder tanks reaches 550 kPa (80 psi), the pressure protection valve allows air to flow to the parking and secondary brake tank and the accessory circuits (horn and air seat). All tanks have a check valve at the air supply port to prevent a loss of air if a leak upstream of the tanks occurs. The air system pressure sensor provides an input signal to the Caterpillar Monitoring System, which informs the operator if the air system pressure is low.

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173

Brake Systems • Manual retarder valve (arrow) - Engages rear service brakes - Modulates brakes better than pedal

The manual retarder valve (arrow) is controlled by the retarder lever in the cab. Normally, the retarder valve blocks air flow to the rear service brake relay valve (see Slide No. 176). When the retarder lever is pulled down, air flows to the rear service brake relay valve [maximum 550 kPa (80 psi)]. The retarder lever is used to modulate rear service brake engagement by metering the amount of air flow to the rear service brake relay valve. The retarder engages the same brakes as the service brake pedal (see Slide No. 39), but is easier to control for brake modulation. NOTE: On trucks with the attachment oil cooled front brakes, the retarder also engages the front brakes.

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6

5

174

1. Service brake valve - Engages front and rear brakes 2. Automatic Retarder Control (ARC) valve • Front brake ON/OFF switch and ratio valve

3. Left double check valve • Service brake and manual retarder engage rear brake relay valve

The service brake valve (1) is controlled by the brake pedal in the cab. Supply air for the service brake valve, the manual retarder valve and the Automatic Retarder Control (ARC) valve (2) is supplied from the bottom port of the service brake valve. When the service brakes are engaged, air flows from the service brake valve to the front brake ON/OFF switch (see Slide No. 35). If the front brake ON/OFF switch is ON, air flows through the front brake ratio valve (see Slide No. 170) to the front brake relay valve (see Slide No. 176). Air from the service brake valve also flows through the left double check valve (3) to the rear brake relay valve (see Slide No. 176). Air from the manual retarder valve also flows through the left double check valve. If the manual retarder and the service brakes are engaged at the same time, air from the system with the highest pressure will flow through the left double check valve to the rear brake relay valve.

4. Right double check valve

With ARC installed, air from the manual retarder valve flows through the right double check valve (4) to the retarder ON switch (5), and through the left double check valve to the stoplight switch and the transmission service/retarder brake switch (see Slide No. 171).

5. Retarder ON switch

The retarder ON switch turns on the amber retarder lamp on the dash in the operator’s station when the manual retarder is ENGAGED (see Slide No. 44).

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The Automatic Retarder Control (ARC) system function is to modulate truck braking (retarding) when descending a long grade to maintain a constant engine speed. On the earlier 777D trucks, the ARC system was installed in parallel with the manual retarder and the service brakes. On the 777D Update trucks, the ARC system is separate from the manual retarder and the service brakes. When the ARC is engaged, air flows from the ARC valve to a separate ARC relay valve (see Slide No. 176). Air also flows from the ARC valve through the right double check valve to the retarder ON switch, and through the left double check valve to the stoplight switch and transmission service/retarder brake switch.

6. Secondary brake valve - Modulates parking brake engagement

The secondary brake valve (6) is controlled by the red pedal in the cab (see Slide No. 39). When the secondary brakes are ENGAGED, air flows from the secondary brake valve to the signal port of an inverter valve (see next slide). The inverter valve then blocks the flow of air from the secondary brake tank to the parking brake release valve (see Slide No. 185). Blocking the air from the parking brake release valve positions the spool in the brake release valve to drain the oil from the parking brakes, which allows the springs in the parking brake to ENGAGE the brakes. The secondary brake valve is used to modulate parking brake engagement by metering the amount of air flow to the parking brake release valve.

• Parking brake valve does not modulate engagement

The parking brake air valve (see Slide No. 38) on the shift console in the cab also controls the flow of air to the brake release valve, but the parking brake air valve does not modulate the parking brake application.

• Secondary and parking brake valves engage brake switch

The parking/secondary brake switch (see Slide No. 170) is located in the supply line to the brake release valve. The secondary brake valve and the parking brake air valve send air to this switch when the parking brakes are released.

INSTRUCTOR NOTE: The ARC system will be discussed in more detail later in this presentation.

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3 2

1

175

1. Primary inverter valve signal port 2. Primary inverter valve

When the secondary brakes are engaged, air flows from the secondary brake valve to the signal port (1) of the primary inverter valve (2). The primary inverter valve then blocks the flow of air from the secondary brake tank to the parking brake release valve and the front brake inverter valve.

• Front and rear brakes engaged by secondary brake pedal

Blocking the air from the parking brake release valve positions the spool in the parking brake release valve to drain the oil from the parking brakes, which allows the springs in the parking brake to ENGAGE the rear brakes. Blocking the air from the front brake inverter valve signal port allows supply air to flow to the front brake master cylinder, which engages the front service brakes.

3. Air horn relay valve

Also shown is the air horn relay valve (3). When the operator depresses the horn switch in the center of the steering wheel, the relay valve is energized and supply air flows to the horn.

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2 4

3 8 5 6 7

1

176

• Trucks with standard caliper disk front brakes and ARC

Shown are some of the brake air lines and valves on trucks with the standard caliper disk front brakes and the ARC system. If the truck has caliper disk front brakes and the ARC system, there are three relay valves. On trucks without the ARC system, there are only two relay valves.

1. Service brake and manual retarder (rear brake) relay valve

The rear brake relay valve (1) receives metered air from only the service brake valve or the manual retarder valve. When the service brakes or manual retarder brakes are ENGAGED, the rear brake relay valve opens and metered air flows from the service brake tank, through the brake cylinder double check valve (2), to the rear brake cylinder.

2. Brake cylinder double check valve 3. ARC relay valve

The ARC relay valve (3) receives metered air from only the Automatic Retarder Control (ARC) valve. When the ARC brake system is ENGAGED, the ARC relay valve opens and metered air flows from the service brake tank, through a pressure protection valve (4) and the brake cylinder double check valve (2), to the rear brake cylinder.

4. ARC relay pressure protection valve

The pressure protection valve (4) prevents a total loss of air pressure in the service brake air system if the ARC relay valve fails. The protection valve opens flow to the ARC relay valve at 380 kPa (55 psi) and closes when the pressure decreases below 310 kPa (45 psi).

• Relay valves reduce braking time

The brake relay valves reduce the time required to engage and release the brakes.

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• Double check valve separates brake systems

The brake cylinder double check valve (2) is used to separate the service brakes and manual retarder brakes from the ARC brake system.

5. Front brake relay valve

The front brake relay valve (5) receives metered air from the service brake valve only if the front brake ON/OFF switch is in the ON position. When the service brakes are ENGAGED and the front brake ON/OFF switch is ON, the front brake relay valve opens and metered air flows from the service brake tank, through the front brake double check valve (6) to the front brake cylinder.

6. Front brake double check valve

The front brake double check valve (6) prevents air from flowing through the front brake inverter valve exhaust port when the service brakes are engaged.

7. Front brake inverter valve

The front brake inverter valve (7) is used to ENGAGE the front brakes when the secondary brake pedal is depressed, even if the front brake ON/OFF switch is OFF.

- Engages front brakes

Supply air from the parking and secondary brake tank is present at the supply passage of the inverter valve. When the secondary brake pedal is depressed, the primary inverter valve behind the cab blocks the flow of air to the signal port of the front brake inverter valve. Removing air pressure from the signal port of the front brake inverter valve allows supply air pressure to flow through the inverter valve and the front brake double check valve (6) to the front brake cylinder to engage the front brakes. 8. Brake oil cooler diverter valve

When the service or retarder brakes are ENGAGED, the brake oil cooler diverter valve (8) allows brake cooling oil to flow through the oil cooler located above the torque converter. Normally, brake cooling oil is diverted around the cooler and goes directly to the brakes. Diverting oil around the cooler provides lower temperature aftercooler air during high power demands (when climbing a grade with the brakes RELEASED, for example).

• Relay valve usage

NOTE: Relay valve usage: - One relay valve: Trucks with the attachment oil cooled front brakes and no ARC system. - Two relay valves: Trucks with the attachment oil cooled front brakes and the ARC system or trucks with the caliper disc front brakes and no ARC system. - Three relay valves: Trucks with the caliper disc front brakes and the ARC system.

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1

2

177

1. Diverter valve temperature switch 2. Diverter valve cold oil solenoid valve

The oil cooler diverter valve is also used to reduce the brake cooling oil pressure at the wheels when the oil is cold. A temperature switch (1) is mounted in the inlet port of the diverter valve. The temperature switch is used to open or close a ground circuit to the cold oil solenoid valve (2). When the temperature of the oil is below 38°C (100°F), the switch is closed and the solenoid valve is ENERGIZED. When the solenoid valve is ENERGIZED, air flows to the diverter valve and oil flows through the oil cooler. The oil cooler restricts oil flow more than the bypass tube, so the pressure at the wheels is reduced but the pressure at the oil cooler relief valve is increased. The increased oil pressure causes the oil cooling relief valve to open. The system warms up faster and the overall flow is reduced. When the system temperature increases to 38°C (100°F), the temperature switch opens and the solenoid valve is DE-ENERGIZED. When the solenoid valve is DE-ENERGIZED, the flow of air to the diverter valve is blocked and brake cooling oil bypasses the oil cooler. When the oil temperature is above 38°C (100°F), the oil cooler diverter valve is controlled solely by service or retarder brake application.

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2 4 5

1

8 7

3

6

178 • Trucks with attachment oil cooled front brakes and ARC

Shown are some of the brake air lines and valves on trucks with the attachment oil cooled front brakes and the ARC system. If the truck has the attachment oil cooled front brakes and the ARC system, there are two relay valves. On trucks without the ARC system, there is only one relay valve.

1. Service brake and manual retarder relay valve

The service brake and manual retarder relay valve (1) receives metered air from only the service brake valve or the manual retarder valve. When the service brakes or manual retarder brakes are ENGAGED, the relay valve opens and metered air flows from the service brake tank through the rear brake cylinder double check valve (2) to the rear brake cylinder and through the front brake cylinder double check valve (3) to the front brake cylinder.

2. Rear brake cylinder double check valve 3. Front brake cylinder double check valve 4. ARC relay valve

The ARC relay valve (4) receives metered air from only the Automatic Retarder Control (ARC) valve. When the ARC brake system is ENGAGED, the ARC relay valve opens and metered air flows from the service brake tank, through a pressure protection valve (5) and the rear brake cylinder double check valve (2) to the rear brake cylinder and through the front brake cylinder double check valve (3) to the front brake cylinder.

5. ARC relay pressure protection valve

The pressure protection valve (5) prevents a total loss of air pressure in the service brake air system if the ARC relay valve fails. The protection valve opens flow to the ARC relay valve at 380 kPa (55 psi) and closes when the pressure decreases below 310 kPa (45 psi).

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• Double check valves separate brake systems

The brake cylinder double check valves (2 and 3) are used to separate the service brakes and manual retarder brakes from the ARC brake system.

6. Front brake double check valve

The front brake double check valve (6) prevents air from flowing through the front brake inverter valve exhaust port when the service brakes are engaged.

7. Front brake inverter valve

The front brake inverter valve (7) is used to ENGAGE the front brakes when the secondary brake pedal is depressed.

- Engages front brakes

Supply air from the parking and secondary brake tank is present at the supply passage of the front brake inverter valve. When the secondary brake pedal is depressed, the primary inverter valve behind the cab blocks the flow of air to the signal port of the front brake inverter valve. Removing air pressure from the signal port of the front brake inverter valve allows supply air pressure to flow through the front brake inverter valve and the front brake double check valve (6) to the front brake cylinder to engage the front brakes.

8. Front brake slack adjuster

On trucks with the attachment oil cooled front brakes, a front brake slack adjuster (8) is located on the frame behind the left front suspension cylinder.

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2 1

179

The brake cylinders operate by air-over-oil. When the metered air enters the brake cylinders, a piston moves down and pressurizes the oil in the bottom of the cylinders. 1. Front brake cylinder

The front brake cylinder (1) is located on the hydraulic tank and supplies oil to the front brakes. On trucks with the standard caliper disc brakes, the pressure oil from the front brake cylinder flows directly to the front brake calipers. On trucks with the attachment oil cooled front brakes, the pressure oil from the front brake cylinder flows to the front brake slack adjuster.

• Front brake cylinder test

The oil-to-air ratio of the front brake cylinder is approximately 11.8 to 1. To test the front brake cylinder, install a gauge in the fitting on top of the brake cylinder. On trucks with the standard caliper disc brakes, install a T-fitting and a gauge in the hose at the brake caliper. On trucks with the attachment oil cooled front brakes, install a gauge on the front slack adjuster pressure tap. On trucks with the standard caliper disc brakes, turn ON the front brake ON/OFF switch . When the service brakes are ENGAGED, if the air pressure in the brake cylinder is 690 kPa (100 psi), the oil pressure at the brake caliper or slack adjuster should be approximately 8130 kPa (1180 psi). When the brakes are RELEASED, both pressures should return to zero.

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• Front brake cylinder does not have an overstroke switch

Keep the service brake ENGAGED for at least one minute. If the oil pressure decreases, air or leakage is present in the system. If an overstroke condition occurs, the problem must be repaired The front brake cylinder does not have an overstroke switch.

2. Brake oil makeup tank

As the brake discs in the brake assemblies wear, more oil is needed from the brake cylinders to compensate for the wear. The makeup oil tank (2) supplies makeup oil for the brake cylinders. Oil from the parking brake release valve provides a continuous supply of oil to the makeup oil tank. Low flow to the makeup tank can cause the makeup oil reserve to decrease and cause the brake cylinders to overstroke.

• Check brake makeup oil flow

To check for makeup oil flow, remove the plug from the top of the makeup oil tank. With the engine at LOW IDLE, a stream of oil filling the tank should be visible. If a stream of oil is not visible, the supply orifice or screen may have a restriction (see Slide No. 185) or pump flow may be low.

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1

2

3

180

1. Rear brake cylinder

The rear brake cylinder (1) supplies oil to the rear brakes. The pressure oil from the rear brake cylinder flows to the rear slack adjuster.

• Rear brake cylinder test

The oil-to-air ratio of the rear brake cylinder is approximately 6.6 to 1. To test the rear brake cylinder, install a gauge in the fitting on top of the brake cylinder and a gauge on the pressure tap on the slack adjuster. When the service brakes are ENGAGED, if the air pressure in the brake cylinder is 690 kPa (100 psi), the oil pressure at the slack adjuster should be approximately 4560 kPa (660 psi). When the brakes are RELEASED, both pressures should return to zero.

2. Brake overstroke switch

Keep the service brakes ENGAGED for at least one minute. If the oil pressure decreases, air or leakage is present in the system. If air is in the system or a loss of oil downstream from the cylinder occurs, the piston in the cylinder will overstroke and cause an indicator rod to extend and open the brake overstroke switch (2). The switch provides an input signal to the Caterpillar Monitoring System, which informs the operator of the condition of the rear brake oil circuit. If an overstroke condition occurs, the problem must be repaired and the indicator rod pushed in to end the warning.

3. Brake cylinder breather

Inspect the condition of the breather (3) for the brake cylinders. Oil should not leak from the breathers. Oil leaking from the breathers is an indication that the oil piston seals in the brake cylinder need replacement. Air flow from the breathers during a brake application is an indication that the brake cylinder air piston seals need replacement.

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BRAKE CYLINDER BRAKES ENGAGED AIR PISTON

INDICATOR ROD

FROM MAKEUP TANK OIL PISTON

AIR INLET

TO SLACK ADJUSTER VALVE SPRING

ROD

181 • Brake cylinder ENGAGED

This sectional view shows the brake cylinder when the brakes are ENGAGED. Air pressure from the brake relay valve enters the air inlet. The air pressure moves the air piston and the attached rod closes the valve in the oil piston. When the valve in the oil piston is closed, the oil piston pressurizes the oil in the cylinder. The pressure oil flows to the rear and front slack adjusters or the front brake calipers.

• Brake overstroke switch indicates loss of brake oil

If air is in the system or a loss of oil downstream from the cylinders occurs, the piston in the cylinder will overstroke and cause the indicator rod to extend and open the brake overstroke switch. The switch provides an input signal to the Caterpillar Monitoring System, which informs the operator of the condition of the service and retarder brake oil circuit. If an overstroke condition occurs, the problem must be repaired and the indicator rod pushed in to end the warning. When the air pressure is removed from behind the air piston, the spring moves the air piston and the attached rod opens the valve in the oil piston. Any makeup oil that is needed flows into the passage at the top of the oil chamber, through the valve, and into the oil chamber at the right of the oil piston.

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2

4

3

1

182

1. Rear slack adjuster

Shown is the rear slack adjuster (1). The slack adjuster compensates for brake disc wear by allowing a small volume of oil to flow through the slack adjuster and remain between the slack adjuster and the brake piston under low pressure. The slack adjusters maintain a slight pressure on the brake piston at all times.

• Cooling oil pressure maintains clearance between discs

Brake cooling oil pressure maintains a small clearance between the brake discs.

2. Service brake pressure tap

The service brake oil pressure can be tested at the tap (2) located on top of the slack adjuster.

3. Right parking brake pressure tap

The brake release pressure for the right parking brake can be tested at the tap (3).

4. Left parking brake pressure tap

The brake release pressure for the left parking brake can be tested at the tap (4).

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BRAKE SLACK ADJUSTER OIL FLOW TO BRAKE CYLINDER

SMALL PISTON

LARGE PISTON

OIL FLOW FROM BRAKE CYLINDER

FROM WHEEL BRAKES

FROM WHEEL BRAKES

TO WHEEL BRAKES

TO WHEEL BRAKES

BRAKES ENGAGED

BRAKES RELEASED

183 • Slack adjuster RELEASED and ENGAGED

This slide shows sectional views of the slack adjuster when the brakes are RELEASED and ENGAGED.

• Large piston moves to ENGAGE brakes

When the brakes are ENGAGED, oil from the brake cylinder enters the slack adjuster and the two large pistons move outward. Each large piston supplies oil to one wheel brake. The large pistons pressurize the oil to the service brake pistons and ENGAGE the brakes.

• Small piston allows makeup oil to brakes

Normally, the service brakes are FULLY ENGAGED before the large pistons in the slack adjuster reach the end of their stroke. As the brake discs wear, the service brake piston will travel farther to FULLY ENGAGE the brakes. When the service brake piston travels farther, the large piston in the slack adjuster moves farther out and contacts the end cover. The pressure in the slack adjuster increases until the small piston moves and allows makeup oil from the brake cylinder to flow to the service brake piston.

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• Brake springs move large pistons to center of slack adjuster

When the brakes are RELEASED, the springs in the service brakes push the service brake pistons away from the brake discs. The oil from the service brake pistons pushes the large pistons in the slack adjuster to the center of the slack adjuster. Makeup oil that was used to ENGAGE the brakes is replenished at the brake cylinder from the makeup tank.

• Large piston spring keeps pressure on service brake piston

The spring behind the large piston causes some oil pressure to be felt on the service brake piston when the brakes are RELEASED. Keeping some pressure on the brake piston provides rapid brake engagement with a minimum amount of brake cylinder piston travel.

• Check slack adjuster for correct operation

The slack adjusters can be checked for correct operation by opening the service brake bleed screw with the brakes RELEASED. A small amount of oil should flow from the bleed screw when the screw is opened. The small flow of oil verifies that the spring behind the large piston in the slack adjuster is maintaining some pressure on the service brake piston. A more accurate test for the slack adjuster is discussed on the next page.

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1 2

184

1. Service brake bleed screw 2. Parking brake bleed screw

The service brake bleed screw (1) is identified by an "S" on the brake anchor plate casting next to the screw. The parking brake bleed screw (2) is identified by a "P" on the casting.

• Slack adjuster test

Another check to verify correct slack adjuster operation is to connect a gauge to the pressure tap on top of the slack adjuster and another gauge at the service brake bleed screw location on the brake anchor plate casting. Use a 5P1404 Adapter (7/8-14 external threads and 9/16-18 internal threads) and a 6V3965 Valved Nipple in the service brake bleed screw location to connect the pressure gauge.

• Brakes RELEASED

With the system air pressure at maximum and the service brake pedal depressed, the pressure reading on both gauges should be approximately the same. When the brakes are RELEASED, the pressure at the slack adjuster should return to zero. The pressure at the service brake bleed screw location should return to the residual pressure held on the brakes by the slack adjuster piston.

• Residual pressure at bleed screw

The residual pressures at the service brake bleed screw location should be: Front (oil cooled): 120 kPa (17.4 psi) Rear: 105 kPa (15.3 psi)

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• Check for warped brake discs

Low residual pressure indicates a failed slack adjuster. High residual pressure may indicate a failed slack adjuster or warped brake discs. To check for warped brake discs, rotate the wheel to see if the pressure fluctuates. If the pressure fluctuates while rotating the wheel, the brake discs are probably warped and should be replaced.

• Check for brake cooling oil leakage

To check for brake cooling oil leakage, block the brake cooling ports and pressurize each brake assembly to a maximum of 138 kPa (20 psi). Close off the air supply source and observe the pressure trapped in the brake assembly for five minutes. The trapped pressure should not decrease.

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1

2

4 3

185

1. Parking brake release valve

Oil from the parking brake release pump (see Slide No. 99) flows through the parking brake release filter (see Slide No. 103) to the parking brake release valve (1). The parking brake release valve is located inside the left frame near the torque converter. Oil flows from the parking brake release valve to the parking brake piston in the rear brakes when the parking brakes are released.

2. Brake release valve air supply hose

Supply air from the parking brake air valve in the cab or the secondary brake valve flows through the small hose (2) to an air chamber in the brake release valve. The brake release valve contains an air piston that moves a spool. The spool either directs oil to RELEASE the parking brakes or drains oil to ENGAGE the parking brakes. A relief valve (3) in the bottom of the brake release valve limits the system pressure for releasing the brakes. The setting of the relief valve is 4700 ± 200 kPa (680 ± 30 psi)

3. Brake release relief valve

4. Brake oil makeup tank supply orifice and screen

Supply oil flows from the parking brake release valve through an orifice and a screen (4) to the brake oil makeup tank (see Slide No. 179).

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3

2

186

1. Electric motor 2. Towing pump

Shown is the area behind the right front suspension cylinder. To release the parking brakes for service work or towing, the electric motor (1) can be energized by the brake release switch located in the cab (see Slide No. 46). The motor drives a pump (2) which sends oil through a diverter (towing) valve to the brake release valve to RELEASE the parking brakes. Towing pump pressure is limited by the relief valve in the brake release valve.

• Air pressure needed to release brakes for towing

Air pressure is also needed to release the brakes for towing. The piston chamber in the brake release valve must be pressurized to move the spool in the valve. The oil from the electrically driven brake release pump can then flow to the rear brakes.

3. Secondary steering pump

The pump (3) on the right supplies flow to the secondary steering system (see Slide No. 140).

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187

• Diverter valve (arrow)

The diverter (towing) valve (arrow) must be shifted before towing. The diverter valve is located on the left hoist cylinder frame support.

• Towing pump oil flows to tank during secondary steering test

When the key start switch is turned ON, the secondary steering system is energized for three seconds to check the system. Since the towing pump is driven by the same electric motor as the secondary steering pump, the diverter valve allows the towing pump oil to flow directly to the hydraulic tank during the secondary steering test.

• Shift diverter valve for towing

To shift the diverter valve, loosen the two diverter valve clamp bolts and slide the plate and the spool to the left. After the spool is shifted, tighten the diverter valve clamp bolts. When the electric motor is energized, supply oil can flow from the towing pump, through the diverter valve, to the parking brake release valve.

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• Procedure to check parking brake release system for towing

To check the brake release system used for towing, install a gauge on a parking brake pressure tap on the rear axle (see Slide No. 182). Use a long gauge hose so the gauge can be held in the cab. With the parking brake air valve in the RELEASE position and the key start switch in the ON position, energize the parking brake release switch used for towing on the dash. The parking brake release pressure should increase to 4700 ± 200 kPa (680 ± 30 psi). This pressure is the setting of the relief valve in the brake release valve. Turn off the switch when the pressure stops increasing.

• Parking brake release pressures

The parking brakes start to release between 3100 and 3445 kPa (450 and 500 psi). Parking brake release pressure must not be below these pressure or the brakes will drag. The parking brakes are fully released between 3445 and 3860 kPa (500 and 560 psi).

NOTE: At least 550 kPa (80 psi) air pressure must be available at the parking brake release valve to ensure full release of the brakes for towing.

NOTICE Energize the brake release switch only when additional pressure is required to release the brakes. Leaving the brake release (towing) motor energized continuously will cause damage to the motor. The parking brake release pressure setting must not exceed 5445 kPa (790 psi). Exceeding this pressure can cause internal damage to the brake assembly.

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BRAKE RELEASE

AIR SUPPLY FROM PARKING BRAKE AIR SWITCH

DURING TOWING

PARKING BRAKE RELEASE VALVE

RELIEF VALVE HOIST VALVE PILOT SUPPLY

PARKING BRAKE RELEASE PUMP AND FILTER

CHECK VALVE

DIVERTER VALVE

DIVERTER VALVE CLAMP BOLTS

TOWING PUMP

SECONDARY STEERING PUMP

188 • Parking brake system - During towing

Shown is a schematic of the parking brake system during TOWING with the parking brakes released.

• Towing pump energized by secondary steering/ brake release switch

To release the parking brakes for service work or towing, an electric motor can be energized with the secondary steering/brake release switch on the dash in the cab. The electric motor then drives two pumps. One pump provides supply oil for releasing the parking brakes, and the second pump supplies oil for secondary steering.

• Diverter valve must be shifted before towing

As previously stated, the diverter valve must be shifted before the towing pump can supply oil to the parking brake system. To shift the diverter valve, loosen the two diverter valve clamp bolts and slide the plate and the spool to the left. After the spool is shifted, tighten the diverter valve clamp bolts. When the electric motor is energized, supply oil will flow from the towing pump, through the diverter valve, to the parking brake release valve.

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• Check valve prevents flow to parking brake release pump

A check valve prevents towing pump supply oil from flowing to the normal parking brake release pump.

• Air supply required for towing

Towing supply oil flows through the parking brake release valve to release the parking brakes as long as supply air is available from the parking brake air valve in the cab.

• Brake release pressure limited by relief valve in parking brake release valve

During towing and normal operation, the brake release pressure is limited by the relief valve located in the parking brake release valve.

NOTE: Before normal operation of the parking brake release system can occur, the diverter valve must be shifted back to its normal operating position.

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PARKING/SECONDARY BRAKE SYSTEM SECONDARY BRAKES ENGAGED RELAY VALVE (FRONT) PARKING BRAKE AIR VALVE

PARKING/ SECONDARY BRAKE SWITCH

DOUBLE CHECK VALVE

FRONT BRAKE INVERTER VALVE

BRAKE CYLINDER ( FRONT ) BRAKE RELEASE VALVE

PRIMARY INVERTER VALVE SECONDARY BRAKE VALVE

HOIST VALVE PILOT SUPPLY

189 • Parking/secondary brake system

Shown is the parking and secondary brake system with the secondary brakes ENGAGED.

• Secondary brake valve controls air flow to:

Supply air from the parking and secondary brake tank is present at the supply passage of the secondary brake valve, the primary inverter valve and the front brake inverter valve. When the secondary brake pedal is depressed, air flows to the signal port of the primary inverter valve. The primary inverter valve then blocks the flow of air to the parking brake air valve, the parking and secondary brake switch, the parking brake release valve and the signal port of the front brake inverter valve.

- Parking brake air valve - Parking/secondary brake switch - Parking brake release valve - Front brake inverter valve

Removing air pressure from the parking and secondary brake switch causes the Transmission/Chassis ECM to eliminate the anti-hunt timer and allow rapid downshifts.

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Removing air pressure from the parking brake release valve allows oil from the parking brake to drain through the brake release valve. The springs in the parking brake then ENGAGE the brakes. Removing air pressure from the signal port of the front brake inverter valve allows supply air pressure to flow through the front brake inverter valve and the double check valve to the front brake cylinder to engage the front brakes. The double check valve prevents air from flowing through the front brake inverter valve exhaust port when the service brakes are engaged.

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SERVICE/RETARDER BRAKE SYSTEM (CALIPER DISK FRONT BRAKES) FRONT BRAKE VALVE OFF SERVICE BRAKES ENGAGED RETARDER RELEASED ARC OFF AIR TANK (SERVICE)

BRAKE CYLINDER ( REAR )

RELAY VALVE (REAR BRAKE)

AIR TANK (SERVICE) AIR PRESSURE SENSOR

CAB ENCLOSURE FRONT BRAKE ON/OFF SERVICE VALVE BRAKE CONTROL VALVE

PRESSURE PROTECTION VALVE

RETARDER VALVE FRONT BRAKE RATIO VALVE

RELAY VALVE (ARC)

BRAKE CYLINDER ( FRONT ) FRONT BRAKE INVERTER VALVE ARC VALVE RETARDER SWITCH

OIL COOLER DIVERTER VALVE

RELAY VALVE (FRONT)

COLD OIL SOLENOID VALVE

STOP LIGHT AND TRANSMISSION SERVICE/RETARDER SWITCH

190 • Service/retarder brake air system - Caliper disk front brakes

This schematic shows the flow of air through the service and retarder brake air system on trucks with caliper disk front brakes. In this schematic, the front brake ON/OFF valve is in the OFF position and the service brake control valve is ENGAGED. The retarder valve is in the RELEASED position and the ARC is OFF. Supply air pressure flows from the service brake air tanks to the relay valves, the cold oil solenoid valve and through the air system pressure sensor to the service brake valve. Supply air pressure flows from the service brake valve to the retarder valve and the ARC valve. The retarder valve blocks the flow of air to three double check valves. The ARC valve blocks the flow of air to two double check valves and the ARC relay valve.

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• Front brake ON/OFF valve controls air flow to front brake cylinder

With the front brake ON/OFF switch in the OFF position and the service brake pedal depressed, only the rear service brakes are ENGAGED. Air flows from the service brake control valve to the front brake ON/OFF valve and is blocked.

• Service brake energizes two brake switches

Air also flows from the service brake control valve, through a double check valve, to the stoplight switch and the transmission service and retarder brake switch. Depressing the service brake pedal turns ON the brake lights and changes the transmission shift points and anti-hunt timer. Air also flows from the service brake control valve, through a double check valve, to the rear brake relay valve. The rear brake relay valve opens and allows air from the service brake tanks to flow through a double check valve to the rear brake cylinder. Air from the rear brake relay valve compresses the piston in the rear brake cylinder and ENGAGES the rear brakes.

• Manual retarder operation - Energizes three brake switches

- Engages only rear brakes

• ARC operation - Energizes three brake switches

When the retarder lever is moved, air flows through three double check valves. Air flows from the retarder valve through a double check valve next to the ARC valve and through a double check valve next to the brake switches. Pulling the retarder lever turns ON the retarder dash lamp, the brake lights, and changes the transmission shift points and anti-hunt timer. Air also flows from the retarder valve, through a double check valve, to the rear brake relay valve. Only the rear brakes are ENGAGED when the retarder is ENGAGED. When the ARC is energized, air flows through two double check valves. Air flows from the ARC valve, through a double check valve next to the ARC valve, and through a double check valve next to the brake switches. Energizing the ARC turns ON the retarder dash lamp, the brake lights, and changes the transmission shift points and anti-hunt timer.

- Engages only rear brakes

Air also flows from the ARC valve to the ARC relay valve. The ARC relay valve opens and allows air from the service brake tanks to flow through a pressure protection valve and a double check valve to the rear brake cylinder. Only the rear brakes are ENGAGED when the ARC is energized.

- Pressure protection valve

The pressure protection valve prevents a total loss of air pressure in the service brake air system if the ARC relay valve fails. The protection valve opens to permit flow to the ARC relay valve at 380 kPa (55 psi) and closes when the pressure decreases below 310 kPa (45 psi).

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When the service or retarder (manual or auto) brakes are ENGAGED, air flows through a double check valve to the brake oil cooler diverter valve. The brake oil cooler diverter valve allows brake cooling oil to flow through the oil cooler located above the torque converter. Normally, brake cooling oil is diverted around the cooler and goes directly to the brakes. Diverting oil around the cooler provides lower temperature aftercooler air during high power demands (when climbing a grade with the brakes RELEASED, for example).

• Diverter valve temperature switch • Diverter valve cold oil solenoid valve

The oil cooler diverter valve is also used to reduce the brake cooling oil pressure at the wheels when the oil is cold. A temperature switch is mounted in the inlet port of the diverter valve. The temperature switch is used to open or close a ground circuit to the cold oil solenoid valve. When the temperature of the oil is below 38°C (100°F), the switch is closed and the solenoid valve is ENERGIZED. When the solenoid valve is ENERGIZED, air flows to the diverter valve and oil flows through the oil cooler. The oil cooler restricts oil flow more than the bypass tube, so the pressure at the wheels is reduced but the pressure at the oil cooler relief valve is increased. The increased oil pressure causes the oil cooling relief valve to open. The system warms up faster and the overall flow is reduced. When the system temperature increases to 38°C (100°F), the temperature switch opens and the solenoid valve is DE-ENERGIZED. When the solenoid valve is DE-ENERGIZED, the flow of air to the diverter valve is blocked and brake cooling oil bypasses the oil cooler. When the oil temperature is above 38°C (100°F), the oil cooler diverter valve is controlled solely by service or retarder brake application.

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SERVICE/RETARDER BRAKE SYSTEM (OIL COOLED FRONT BRAKES) SERVICE BRAKES RELEASED RETARDER ENGAGED ARC OFF BRAKE CYLINDER ( REAR )

AIR TANK (SERVICE)

OIL COOLER DIVERTER VALVE

AIR TANK (SERVICE) PRESSURE PROTECTION VALVE

CAB ENCLOSURE RETARDER VALVE SERVICE BRAKE CONTROL VALVE

AIR PRESSURE SENSOR

RELAY VALVE (ARC)

BRAKE CYLINDER ( FRONT ) FRONT BRAKE INVERTER VALVE ARC VALVE RETARDER SWITCH

RELAY VALVE (SERVICE AND MANUAL RETARD)

COLD OIL SOLENOID VALVE

STOP LIGHT AND TRANSMISSION SERVICE/RETARDER SWITCH

191 • Service/retarder brake air system - Oil cooled front brakes

This schematic shows the flow of air through the service and retarder brake air system on trucks with the attachment oil cooled front brakes. In this schematic, the service brake control valve is RELEASED. The retarder valve is in the ENGAGED position and the ARC is OFF. Supply air pressure flows from the service brake air tanks to the relay valves, the cold oil solenoid valve and through the air system pressure sensor to the service brake valve. Supply air pressure flows from the service brake valve to the retarder valve and the ARC valve. The service brake valve blocks the flow of air to two double check valves and the service and manual retarder relay valve. The ARC valve blocks the flow of air to two double check valves and the ARC relay valve. NOTE: On trucks with the attachment oil cooled front brakes and no ARC, there will be only one relay valve.

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Air flows from the manual retarder valve, through a double check valve, to the retarder switch, the stoplight switch and the transmission service and retarder brake switch. Pulling the retarder lever turns ON the retarder dash lamp, the brake lights and changes the transmission shift points and anti-hunt timer. Air also flows from the retarder valve, through a double check valve, to the service and manual retarder relay valve. The relay valve opens and allows air from the service brake tanks to flow through through two double check valves to the front and rear brake cylinders.

- Engages front and rear brakes

On trucks with the attachment oil cooled front brakes, the front and rear brakes are engaged when the manual or auto retarder is ENGAGED.

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BRAKE COOLING SYSTEM CALIPER DISC FRONT BRAKES REAR BRAKES

HOIST VALVE

DIVERTER VALVE

BRAKE OIL COOLER TO BRAKE MAKEUP TANK

TORQUE CONVERTER CHARGING FILTER INLET RELIEF VALVE

HOIST PUMP

HOIST, CONVERTER AND BRAKE OIL COOLER

192 • Brake oil cooling system--caliper disc front brakes • Three pump sections for rear brake cooling:

This schematic shows the flow of oil through the brake cooling system on the 777D Update trucks with caliper disc front brakes. Three pump sections provide oil for rear brake cooling: the hoist pump and the torque converter charging and brake release sections of the torque converter pump. All the pumps pull oil from the hydraulic tank through suction screens.

• Hoist pump flow

Oil flows from the hoist pump to the hoist valve. In the HOLD, FLOAT and SNUB positions, oil from the hoist pump flows through the hoist valve to the rear brake cooling system.

• Oil cooling relief valve

The pressure in the brake cooling system is limited by a relief valve located in the hoist valve. The setting of the brake oil cooling relief valve is 586 ± 14 kPa (85 ± 2 psi). The relief valve is usually needed only when the brake cooling oil is cold. When brake cooling oil is at operating temperature, the brake cooling oil pressure is usually much lower than the setting of the oil cooling relief valve.

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• Converter charging pump flow

Oil flows from the torque converter charging pump through the torque converter charging filter and the torque converter to the hoist, converter and brake oil cooler located on the right side of the engine. Oil flows through the cooler to the rear brakes.

• Brake release pump flow

Oil flows from the brake release pump through the brake release filter to the brake release valve. The brake release valve controls the oil pressure to release the parking brakes, lock up the torque converter and shift the directional spool in the hoist valve. These functions require minimal oil flow. Most of the oil from the brake release pump flows through the brake release valve and joins with the torque converter charging pump oil at the torque converter inlet relief valve.

• Brake cylinder oil makeup tank

Supply oil flows from the parking brake release valve through an orifice and a screen to the brake oil makeup tank (see Slide No. 179). The makeup tank provides a continuous supply of oil to the brake cylinders. The brake cylinders require more oil as the brakes wear.

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BRAKE COOLING SYSTEM OIL COOLED FRONT BRAKES RIGHT REAR BRAKES

FRONT BRAKES HOIST VALVE

LEFT

DIVERTER VALVE BRAKE OIL COOLER

TO BRAKE MAKEUP TANK

PARKING BRAKE RELEASE VALVE HOIST PUMP

TORQUE CONVERTER CHARGING FILTER INLET RELIEF VALVE

HOIST, CONVERTER AND BRAKE OIL COOLER

193 • Brake oil cooling system--oil cooled front brakes • Four pump sections for brake cooling:

This schematic shows the flow of oil through the brake cooling system on the 777D Update trucks with oil cooled front brakes. Four pump sections provide oil for front and rear brake cooling: the hoist pump and the torque converter charging, brake release and brake cooling sections of the torque converter pump. All the pumps pull oil from the hydraulic tank through suction screens.

• Hoist pump flow

Oil flows from the hoist pump to the hoist valve. In the HOLD, FLOAT and SNUB positions, oil from the hoist pump flows through the hoist valve to the front and rear brake cooling system.

• Oil cooling relief valve

The pressure in the brake cooling system is limited by a relief valve located in the hoist valve. The setting of the brake oil cooling relief valve is 586 ± 14 kPa (85 ± 2 psi). The relief valve is usually needed only when the brake cooling oil is cold. When brake cooling oil is at operating temperature, the brake cooling oil pressure is usually much lower than the setting of the oil cooling relief valve.

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• Converter charging pump flow

Oil flows from the torque converter charging pump through the torque converter charging filter and the torque converter to the hoist, converter and brake oil cooler located on the right side of the engine. Oil flows through the cooler to the rear brakes.

• Brake release pump flow

Oil flows from the brake release pump through the brake release filter to the brake release valve. The brake release valve controls the oil pressure to release the parking brakes, lock up the torque converter and shift the directional spool in the hoist valve. These functions require minimal oil flow. Most of the oil from the brake release pump flows through the brake release valve and flows through both oil coolers to the front and rear brakes. Some of the oil flows through the hoist, converter and brake oil cooler and some of the oil flows through the brake oil cooler.

• Brake cylinder oil makeup tank

Supply oil flows from the parking brake release valve through an orifice and a screen to the brake oil makeup tank (see Slide No. 179). The makeup tank provides a continuous supply of oil to the brake cylinders. The brake cylinders require more oil as the brakes wear.

• Brake cooling pump flow

The brake cooling pump section of the torque converter pump sends additional oil through the hoist, converter and brake oil cooler located on the right side of the engine to the rear brakes.

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1

2

3

194

• Brake oil cooler used only with brakes ENGAGED 1. Diverter valve 2. Brake oil cooler

When the service or retarder brakes are ENGAGED, the brake oil cooler diverter valve (1) allows brake cooling oil to flow through the brake oil cooler (2). When the brakes are RELEASED, the oil bypasses the cooler and flows directly to the brakes. The brake oil cooler is cooled by the engine aftercooler cooling system. Normally, brake cooling oil is diverted around the cooler and goes directly to the brakes. Diverting oil around the cooler provides lower temperature aftercooler air during high engine power demands.

• Diverter valve reduces brake pressure at wheels 3. Temperature switch

The brake oil cooler diverter valve is also used to reduce the brake cooling oil pressure at the wheels when the oil is cold. A temperature switch (3) is mounted in the inlet port of the diverter valve. The temperature switch is used to open or close a ground circuit to the cold oil solenoid valve (see Slide No. 177). When the temperature of the oil is below 38°C (100°F), the switch is closed and the solenoid valve is ENERGIZED. When the solenoid valve is ENERGIZED, air flows to the diverter valve and oil flows through the oil cooler. The oil cooler restricts oil flow more than the bypass tube, so the pressure at the wheels is reduced but the pressure at the oil cooler relief valve is increased. The increased oil pressure causes the oil cooling relief valve to open. The system warms up faster and the overall flow is reduced. When the system temperature increases to 38°C (100°F), the temperature switch opens and the solenoid valve is DE-ENERGIZED. When the solenoid valve is DEENERGIZED, the flow of air to the diverter valve is blocked and brake cooling oil bypasses the oil cooler.

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195

• Brake cooling oil pressure taps (arrows)

Shown is the left rear brake housing on a 777D Update truck. Brake cooling oil pressure can be tested at the two taps (arrows) located in the brake cooling oil tubes. One tap is located on the brake cooling inlet tube and another tap is located on the brake cooling outlet tube. The pressure measured at the brake inlet tube (from the oil coolers) will always be higher than the pressure measured at the brake outlet tube.

• Brake cooling oil pressure

With the brake cooling oil temperature between 79 and 93°C (175 and 200°F), the pressure at the brake inlet tube should be above 14 kPa (2 psi) at LOW IDLE and below 172 kPa (25 psi) at HIGH IDLE.

• High brake cooling oil temperature

A brake oil temperature sensor is located in a brake oil cooling tube on the truck. The brake oil temperature sensor provides input signals to the Caterpillar Monitoring System, which keeps the operator informed of the brake cooling oil temperature.

- Gear range too high

The most common cause of high brake cooling oil temperature is operating the truck in a gear range which is too high for the grade and not maintaining a high enough engine speed. The engine speed should be maintained at approximately 1900 rpm during long downhill hauls.

- Engine speed too low - Relief valve stuck open

Make sure the oil cooling relief valve is not stuck open.

- Slack adjuster pistons stuck

Also, make sure the pistons in the slack adjuster are not stuck and holding too much pressure on the brakes (see Slides No. 182 and 183).

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BRAKE ELECTRONIC CONTROL SYSTEM

INPUT COMPONENTS CAT DATA LINK ELECTRONIC SERVICE TOOL ENGINE ECM TRANSMISSION/CHASSIS ECM CATERPILLAR MONITORING SYSTEM ECM LOCATION CODE

SHIFT LEVER SWITCH

LEFT BRAKE RELEASE PRESSURE SENSOR

THROTTLE SENSOR

ACTUAL GEAR SWITCH

ENGINE SPEED/TIMING SENSOR PARKING/SECONDARY BRAKE SWITCH

RIGHT BRAKE RELEASE PRESSURE SENSOR

ARC

SERVICE/RETARDER BRAKE SWITCH

OUTPUT COMPONENTS

ENGINE OUTPUT SPEED SENSOR

ARC SUPPLY SOLENOID

ON INPUT

ARC

ARC CONTROL SOLENOID

OFF INPUT ARC ON/OFF SWITCH

TRANSMISSION OUTPUT SPEED SENSOR

RETARDER PRESSURE SWITCH

RETARDER ENGAGED LAMP

AUTO RETARDER PRESSURE SWITCH

TCS

TCS ENGAGED LAMP

TCS TEST SWITCH

TCS SELECTOR SOLENOID (LEFT AND RIGHT)

TCS

LEFT WHEEL SPEED SENSOR PROPORTIONAL (SERVO) SOLENOID

RIGHT WHEEL SPEED SENSOR

196 BRAKE ELECTRONIC CONTROL SYSTEM • Brake electronic control system

The 777D Update trucks are equipped with an electronic control module for controlling both the Automatic Retarder Control (ARC) and the Traction Control System (TCS). Three possible arrangements can be installed on a truck: - ARC only - TCS only - ARC and TCS

• Flash files required

Each arrangement requires a separate "flash" file to tell the control which arrangement is installed. Therefore, three separate flash file part numbers are available, and the flash file which is used depends on the hardware installed on the truck.

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The Brake ECM receives information from various input components such as the Engine Output Speed (EOS) sensor, retarder pressure switch, left and right wheel speed sensors and the TCS test switch. Based on the input information, the Brake ECM determines when the service and retarder brakes should ENGAGE for the ARC or the parking and secondary brakes should ENGAGE for the TCS. These actions are accomplished by sending signals to various output components. Output components include the ARC supply and control solenoids, the retarder ENGAGED lamp, the TCS selector and proportional solenoids and the TCS ENGAGED lamp. The Brake ECM also provides the service technician with enhanced diagnostic capabilities through the use of onboard memory, which stores possible diagnostic codes for retrieval at the time of service.

• Benefits of electronic communication

The Engine ECM, the Transmission/Chassis ECM, the Caterpillar Monitoring System and the Brake ECM all communicate through the CAT Data Link. Communication between the electronic controls allows the sensors of each system to be shared.

• Service tool functions

The Electronic Control Analyzer Programmer (ECAP) and the Electronic Technician (ET) Service Tools can be used to perform several diagnostic and programming functions. Some of the diagnostic and programming functions that the service tools can perform are: - Display the real time status of the input and output parameters. - Display the internal clock hour reading. - Display the number of occurrences and the hour reading of the first and last occurrence for each logged diagnostic code and event. - Display the definition for each logged diagnostic code and event. - Display the supply and control solenoid engagement counter. - Program the ARC control speed. - Perform ARC diagnostic tests. - Upload new Flash files.

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INSTRUCTOR NOTE: Some of the Brake Electronic Control System input and output components are shown during the discussion of other systems. See the following slide numbers: 127. 203. 203. 199. 46. 200. 200. 46. 202. 202. 55. 60. 127. 41. 128. 129. 131. 38. 63. 130. 131. 200. 200. 44. 44. 203. 203. 203.

ECM location code Left brake release pressure sensor Right brake release pressure sensor Engine output speed sensor ARC ON/OFF switch Retarder pressure switch Auto retarder pressure switch TCS test switch Left wheel speed sensor Right wheel speed sensor CAT Data Link/Electronic Service Tool Engine ECM Transmission/Chassis ECM Caterpillar Monitoring System Shift lever switch Actual gear switch Parking/Secondary brake pressure switch Throttle position sensor Engine speed timing sensor Transmission output speed sensor Service/Retarder brake pressure switch ARC supply solenoid ARC control solenoid Retarder engaged lamp TCS engaged lamp TCS selector solenoid (left) TCS selector solenoid (right) TCS proportional (servo) solenoid

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197

• Brake ECM (arrow) - No diagnostic window - Diagnostics and programming require ECAP or ET

• Brake ECM looks like engine ECM

The Brake ECM (arrow) is located in the compartment at the rear of the cab. The Brake ECM does not have a diagnostic window like the ARC and the TCS used on the earlier 777D trucks. All diagnostic and programming functions must be performed with an Electronic Control Analyzer Programmer (ECAP) or a laptop computer with the Electronic Technician (ET) software installed. ET is the tool of choice because the Brake ECM can be reprogrammed with a "flash" file using the WinFlash application of ET. The ECAP cannot upload "flash" files. The Brake ECM looks like the Engine ECM with two 40-pin connectors, but the Brake ECM does not have fittings for cooling fluid. Also, the Brake ECM has no access plate for a personality module.

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AUTOMATIC RETARDER CONTROL BRAKE ECM (ARC) (TCS)

ENGINE SPEED SENSOR ON INPUT ARC ON/OFF SWITCH OFF INPUT SERVICE TOOL ENGINE ECM TRANSMISSION/ CHASSIS ECM MESSAGE CENTER

CAT DATA LINK RETARDER ENGAGED LAMP

SUPPLY SOLENOID VENT

AIR FROM SERVICE BRAKE RESERVOIR

VENT CONTROL SOLENOID

SERVICE BRAKE VALVE

TO SERVICE/ RETARDER BRAKE RELAY VALVE

AUTOMATIC RETARDER VALVE

MANUAL RETARDER VALVE

AUTO RETARDER PRESSURE SWITCH

RETARDER PRESSURE SWITCH

TO ARC RELAY VALVE

198 Automatic Retarder Control (ARC) • Automatic Retarder Control (ARC)

The Automatic Retarder Control (ARC) system function is to modulate truck braking (retarding) when descending a long grade to maintain a constant engine speed. The ARC system engages the service/retarder brakes. If the ON/OFF switch is moved to the ON position, the ARC will be activated if the throttle pedal is not depressed and the parking/ secondary brakes are RELEASED. The ARC system is disabled when the throttle is depressed or when the parking/secondary brakes are ENGAGED. The ARC is not connected to the service brakes and the manual retarder. When the ARC is ENGAGED, air flows from the ARC valve to a separate relay valve (see Slides No. 190 and 191).

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The ARC is set at the factory to maintain a constant engine speed of 1900 ± 50 rpm (engine speed setting is programmable). When the ARC initially takes control of retarding, the engine speed may oscillate out of the ± 50 rpm target, but the engine speed should stabilize within a few seconds. For proper operation of the ARC, the operator needs only to activate the control with the ARC ON/OFF switch and select the correct gear for the grade, load, and ground conditions. The ARC is designed to allow the transmission to upshift to the gear selected by the shift lever. After the transmission shifts to the gear selected by the operator and the engine speed exceeds 1900 rpm, the ARC will apply the retarder as needed to maintain a constant engine speed.

• ARC provides engine overspeed protection

The ARC system also provides engine overspeed protection. If an unsafe engine speed is reached, the ARC will engage the brakes, even if the ARC ON/OFF switch is in the OFF position and the throttle is depressed. Trucks approaching an overspeed condition will sound a horn and activate a light at 2100 rpm. If the operator ignores the light and horn, the ARC will engage the retarder at 2180 rpm. If the engine speed continues to increase, the Transmission/Chassis ECM will either upshift (one gear only above shift lever position) or unlock the torque converter (if the shift lever is in the top gear position) at 2300 rpm.

• ARC provides programming and diagnostic capability

The ARC also provides service personnel with enhanced diagnostic capabilities through the use of onboard memory, which stores possible faults, solenoid cycle counts and other service information for retrieval at the time of service. By using an ECAP or a laptop computer with the Electronic Technician (ET) software installed, service personnel can access the stored diagnostic information or set the adjustable engine speed control setting. The Auto Retarder Control receives signals from several switches and sensors. The control analyzes the various input signals and sends signals to the output components. The output components are two solenoids and a lamp. INSTRUCTOR NOTE: For more detailed information about the Automatic Retarder Control (ARC) system, refer to the Service Manual Module "Off-Highway Truck/Tractors Brake Electronic Control System" (Form SENR1503) and the Technical Instruction Module "Automatic Retarder Control System" (Form SEGV2593).

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1

2

199

1. Engine output speed sensor

Shown is the location of the Engine Output Speed (EOS) sensor (1) that provides the primary input signal used by the ARC. The engine speed information is the main parameter that the Brake ECM uses to control retarding. The engine speed sensor is a frequency sensor that generates an AC signal from the passing flywheel gear teeth.

2. Engine speed/timing sensor

The engine speed/timing sensor (2) is also used by the ARC for diagnostic purposes. If the Brake ECM receives an input signal from the engine speed/timing sensor, but not the EOS sensor, the Brake ECM will log an engine speed fault. The ARC will not function without an engine speed signal from EOS sensor (1).

• Use 8T5200 Signal Generator to simulate engine speed

NOTE: The 8T5200 Signal Generator/Counter Group can be connected to the engine speed sensor wiring harness and be used to simulate engine speed for diagnostic purposes. To connect the 8T5201 Signal Generator to the engine speed sensor wiring harness, fabricate jumper wires and connect the 8T5198 Adapter Cable (part of the 8T5200 Signal Generator/Counter Group) to the speed sensor harness Deutsch DT connector. 8T5198 Adapter

Deutsch DT Connector

Pin B Pin C

J765 BU Pin 2 (ground) 450 YL Pin 1 (signal)

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4

5

2 1

3

200

1. Retarder pressure switch

Shown is the location of the retarder pressure switch (1). The retarder pressure switch signals the Brake ECM when manual or automatic retarder air pressure is present. The switch is normally open and closes when the manual or automatic retarder is engaged. A fault is recorded when the Brake ECM detects the absence of retarder pressure (switch open) while the supply solenoid and the control solenoid are energized.

2. Auto retarder pressure switch 3. Automatic retarder valve

The auto retarder pressure switch (2) signals the Brake ECM when air pressure is present and the automatic retarder valve (3) is functioning. The auto retarder pressure switch is located in front of the cab in the output port of the automatic retarder valve. The switch is normally closed and opens only when the auto retarder is engaged. A fault is recorded when the Brake ECM detects the presence of auto retarder pressure (switch open) while the supply solenoid and the control solenoid are not energized.

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The supply solenoid valve (4) turns ON or OFF to control the flow of supply air to the automatic retarder valve (3). The Brake ECM energizes the supply solenoid valve with +Battery voltage (24 Volts) at 100 rpm less than the programmed control speed setting. Normally, the reduced speed will be 1800 rpm, since the control speed is set to 1900 rpm at the factory. A fault is recorded if the Brake ECM senses the signal to the supply solenoid as open, shorted to ground, or shorted to battery.

5. Control solenoid valve

The control solenoid valve (5) modulates the air flow to the brakes during automatic retarding. The control solenoid receives a Pulse Width Modulated (PWM) signal from the Brake ECM. The longer the duty cycle, the more time the control solenoid valve is open, and more air pressure is allowed to the brakes. Voltage to the control solenoid increases proportionally from zero to approximately 22 Volts with the demand for more brake pressure. A fault is recorded if the Brake ECM senses the signal to the control solenoid as open, shorted to ground, or shorted to battery.

• Supply and control solenoid resistance

Normal resistance through the supply and control solenoids is 31 Ohms. An excess resistance of approximately 40 Ohms will prevent the valves from opening and will cause a supply or control valve fault to be logged. Therefore, a measurement of approximately 71 Ohms or more will show that the solenoid is defective.

• ARC valve malfunction

The Brake ECM can also determine if the solenoid valves have malfunctioned (valves leaking). If air pressure is present at the auto retarder pressure switch when the solenoids are DE-ENERGIZED, the auto retarder pressure switch will signal the Brake ECM that the ARC valve has malfunctioned.

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TRACTION CONTROL SYSTEM BRAKE ECM (ARC/TCS) ELECTRONIC SERVICE TOOL TCS ENGAGED LAMP

SERVICE/RETARDER BRAKE SWITCH TRANSMISSION OUTPUT SPEED SENSOR

TCS SELECTOR SOLENOID LEFT AND RIGHT

CAT DATA LINK

TCS TEST SWITCH PROPORTIONAL SOLENOID

LEFT WHEEL SPEED SENSOR

+ 10V TO WHEEL SENSORS

RIGHT WHEEL SPEED SENSOR

201 Traction Control System (TCS) • TCS uses rear parking/secondary brakes

The Traction Control System (TCS) uses the rear parking/secondary brakes (spring engaged and hydraulically released) to decrease the revolutions of a spinning wheel. The TCS allows the tire with better underfoot conditions to receive an increased amount of torque. The system is controlled by the Brake ECM (see Slides No. 196 and 197). The Brake ECM monitors the drive wheels through three input signals: one at each drive axle, and one at the transmission output shaft. When a spinning drive wheel is detected, the Brake ECM sends a signal to the selector and proportional valves which ENGAGE the brake of the affected wheel. When the condition has improved and the ratio between the right and left axles returns to 1:1, the Brake ECM sends a signal to RELEASE the brake.

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• TCS replaces AETA

The TCS was formerly referred to as the Automatic Electronic Traction Aid (AETA). The operation of the system has not changed. The main differences are the appearance of the ECM, and the TCS is now on the CAT Data Link. Also, the ECAP and ET Service Tools can communicate with the TCS.

• Service/retarder brake switch:

A service/retarder brake switch (see Slide No. 131) provides an input signal to the TCS through the CAT Data Link and performs two functions:

- Stops TCS function

1. When the service brakes or retarder are ENGAGED, the TCS function is stopped.

- Performs diagnostic test

• Brake release pressure sensors

2. The service/retarder brake switch provides the input signal needed to perform a diagnostic test. When the TCS test switch and the retarder lever are ENGAGED simultaneously, the TCS will engage each rear brake independently. Install two pressure gauges on the TCS valve, and observe the pressure readings during the test cycle. The left brake pressure will decrease and increase. After a short pause, the right brake pressure will decrease and increase. The test will repeat as long as the TCS test switch and the retarder lever are ENGAGED. The TCS valve has a left and right brake release pressure sensor. A laptop computer with the ET software installed can also be used to view the left and right parking brake pressures during the test discussed above in function No. 2. When the proportional solenoid is ENERGIZED, ET will show 44% when the brake is FULLY ENGAGED. NOTE: During the diagnostic test, the parking/secondary brakes must be released.

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202

• Wheel speed sensor (arrow)

Shown is the left rear wheel speed sensor (arrow). The TCS monitors the drive wheels through three input speed signals: one at each drive axle, and one at the transmission output shaft.

• TOS sensor disables TCS

The Transmission Output Speed (TOS) sensor (see Slide No. 130) monitors the ground speed of the machine and provides input signals to the TCS through the CAT Data Link. The TCS uses the TOS sensor to disable the TCS when ground speed is above 19.3 km/h (12 mph).

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1

2

3

3

4

4

203

• TCS valve

The Traction Control System (TCS) valve is mounted inside the rear of the left frame rail. Two solenoids are mounted on the valve.

1. Selector solenoid

Electrical signals from the Brake ECM cause the selector solenoid valve (1) to shift and select either the left or right parking brake. If the selector valve shifts to the left parking brake hydraulic circuit, the control oil is drained. The left reducing spool of the control valve can then shift and engage the parking brake. The Brake ECM energizes the selector solenoid valve with + Battery voltage (24 Volts). Normal resistance through the selector solenoid is between 18 and 45 Ohms.

2. Proportional solenoid

The proportional solenoid valve (2) controls the volume of oil being drained from the selected parking brake control circuit. The rate of flow is controlled by a signal from the Brake ECM. The proportional solenoid receives a current between 100 and 680 mA from the Brake ECM. The more current that is sent, the more the proportional solenoid valve is open, and more oil pressure is drained from the brakes. Normal resistance through the solenoid is between 12 and 22 Ohms.

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The pressure taps (3) or pressure sensors (4) can be used to test the left and right brake release pressures when performing diagnostic tests on the TCS. At HIGH IDLE, the pressure at the taps in the TCS valve will be approximately 138 kPa (20 psi) less than the brake release pressure tested at the wheels. The pressure sensors are also used to provide parking brake dragging information to the service technician. If the parking brakes are released, as sensed by the parking brake switch behind the cab, and parking brake pressure is below 3445 kPa (500 psi), a parking brake dragging event will be logged in the Brake ECM. The event can be seen with ET.

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TRACTION CONTROL SYSTEM (TCS) ENGINE RUNNING/BRAKES RELEASED TEST SWITCH SERVICE/RETARDER BRAKE SWITCH

LEFT DRIVE AXLE INPUT SIGNALS

BALL CHECK TRANSMISSION SPEED SENSOR

OUTPUT SIGNALS

ORIFICE

SCREEN

TCS ENGAGED LAMP SELECTOR SOLENOID PARKING BRAKE VALVE

RIGHT DRIVE AXLE PROPORTIONAL SOLENOID

204 • TCS operation with brakes RELEASED

Shown is the TCS with the engine running and the brakes RELEASED. When the machine is started: - Oil flows from parking brake release pump through the brake release oil filter where the flow is divided. One line from the filter directs oil to the parking brake release valve. The other line sends oil to the signal port (right end of signal piston) of the TCS control valve. - Oil flow to the TCS control valve signal port causes the ball check piston to move to the left and unseat the drain ball check valve. Opening the drain ball check valve opens a drain passage to the hydraulic tank.

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When the operator releases the parking brakes: - Air pressure is increased at the parking brake release valve forcing the valve spool down. - Parking brake release oil can now flow through the parking brake release valve to the TCS control valve. - In the control valve, oil closes the parking/secondary ball check valve and flows through the screen. - Oil flows through the right and left brake control circuit orifices. - Oil flows to the ends of the left and right brake reducing valve spools. - When the control circuit pressure is high enough, the reducing spools shift toward the center of the TCS control valve and parking brake release oil flows to release the brakes.

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TRACTION CONTROL SYSTEM (TCS) ENGINE RUNNING/LEFT BRAKE ENGAGED TEST SWITCH SERVICE/RETARDER BRAKE SWITCH

LEFT DRIVE AXLE INPUT SIGNALS

BALL CHECK TRANSMISSION SPEED SENSOR

OUTPUT SIGNALS

ORIFICE

SCREEN

TCS ENGAGED LAMP SELECTOR SOLENOID PARKING BRAKE VALVE

RIGHT DRIVE AXLE PROPORTIONAL SOLENOID

205 • TCS operation with left brake ENGAGED

Shown is the TCS with the engine running and the left brake ENGAGED. When signals from the sensors indicate that the left wheel is spinning 60% faster than the right wheel, the following sequence of events occurs: - The Brake ECM sends a signal to the selector solenoid valve and the proportional solenoid valve. - The selector solenoid valve opens a passage between the outer end of the left brake pressure reducing valve and the proportional solenoid valve. - The proportional solenoid valve opens a passage from the selector solenoid valve to drain. The proportional solenoid valve also controls the rate at which the oil is allowed to drain. - Control circuit oil drains through the selector valve and enters the proportional valve.

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- The reducing valve spool for the left parking brake shifts and blocks the flow of oil to the parking brake. - Oil in the left parking brake control circuit begins to drain. - The left parking brake begins to ENGAGE. - The left brake orifice restricts the flow of oil from the parking brake release valve.

When the signals from the sensors indicate that the left wheel is no longer spinning, the following sequence occurs: - The Brake ECM stops sending signals to the selector solenoid and the proportional solenoid. - The selector solenoid valve and proportional solenoid valve block the passage to drain and allow the control circuit pressure to increase. - The left brake reducing valve spool shifts to the center position and blocks the passage to drain. - Parking brake release oil is directed to the left parking brake and the brake is RELEASED.

INSTRUCTOR NOTE: For more detailed information on the Traction Control System (TCS) refer to the Service Manual module "Off-Highway Truck/Tractors Brake Electronic Control System" (Form SENR1503) and the Technical Instruction Module "Automatic Electronic Traction Aid" (Form SEGV2585).

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206

CONCLUSION This presentation has provided a basic introduction to the Caterpillar 777D Update Off-highway Trucks. All the major component locations were identified and the major systems were discussed. When used in conjunction with the service manual, the information in this package should permit the serviceman to analyze problems in any of the major systems on these trucks.

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SLIDE LIST 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41.

Model view (right side) Model view (left side) Model view (front) Model view (rear) Subtitle slide--Walk around inspection Daily maintenance Front wheel Front Suspension Front brake Primary fuel filter and oil level switch Jacket water coolant S•O•S tap Transmission charge filter Fuel tank Brake cylinder breather Final drive Rear suspension cylinders Body up retaining pin Hydraulic tank and air tanks Left frame filters and air dryer Engine oil filters Engine oil S•O•S tap Engine fuel filters Manual shutdown switch Battery disconnect switch Batteries Radiator top tank Steering tank and filters Air filters Engine oil dipstick Windshield washer reservoir A/C filter Operator's station--right side Operator's station--left side Operator's station--left side Operator's station/instrument panel Operator's station/wiper switch Operator's station/instrument panel Operator's station/operator controls Operator's station/operator controls Hoist lever Caterpillar Monitoring System schematic 42. Dash schematic

43. Caterpillar Monitoring System schematic 44. Operator's station/instrument panel 45. Speed/tach 46. Operator's station/dash switches 47. Operator's station/message center 48. Operator's station/circuit breakers 49. Operator modes 50. Service modes 51. Service sub modes 52. ECM's 53. Cab rear electrical components 54. Cab rear electrical components 55. ET Laptop 56. Payload Operator Display (POD) 57. TPMS Laptop 58. Payload Operator Display (POD) 59. Engine (left side) 60. Engine control inputs/outputs 61. Engine ECM 62. Atmospheric pressure sensor 63. Speed/timing sensor 64. Throttle position sensor 65. Crankcase pressure sensor 66. EUI injector 67. Logged events (text) 68. Engine controlled systems (text) 69. Engine oil pre-lubrication pump 70. Radiator top tank 71. Jacket water pump 72. Thermostat housing and temp sensor 73. Coolant flow switch 74. Oil coolers on engine 75. Jacket water coolant flow schematic 76. Aftercooler water pump 77. Aftercooler and temp sensor 78. Brake oil cooler 79. Aftercooler coolant flow schematic 80. Engine oil pump 81. Engine oil filters 82. Engine oil S•O•S tap 83. Engine oil flow schematic 84. Primary fuel filter and oil level switch

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SLIDE LIST 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99. 100. 101. 102. 103. 104. 105. 106. 107. 108. 109. 110. 111. 112. 113. 114. 115. 116. 117. 118. 119. 120. 121. 122.

Fuel transfer pump Secondary fuel filters Fuel pressure regulator Fuel system circuit Air induction and exhaust system Turbocharger inlet pressure sensor 3508B turbochargers Exhaust temperature sensor Turbocharger outlet pressure sensor 3508B air induction and exhaust system Power train Torque converter Torque converter (converter drive) Torque converter drive (direct drive) Torque converter pump (four sections) Torque converter charging filter Torque converter inlet relief valve Hoist,converter and brake oil cooler Parking brake release oil filter Parking brake release valve Torque converter lockup clutch valve Torque converter lockup clutch control (converter drive) Torque converter lockup clutch control (direct drive) Torque converter hydraulic system (caliper disc front brakes) Torque converter hydraulic system (oil cooled front brakes) Transfer gears Transmission pump Transmission charging filter Transmission clutch control valve Transmission lube pressure tap ICM transmission controls (NEUTRAL sectional view) ICM transmission controls (FOURTH sectional view) ICM valve station (clutch released) ICM valve station (clutch filling) ICM valve station (clutch engaged) ICM valve station (clutch decay) Valve station graph (shift cycle) Valve station graph (problems)

123. 124. 125. 126. 127. 128. 129. 130. 131. 132. 133. 134. 135. 136. 137. 138. 139. 140. 141. 142. 143. 144. 145. 146. 147. 148. 149. 150. 151. 152. 153. 154. 155. 156. 157. 158. 159. 160. 161.

Transmission hydraulic system Rear axle Differential Transmission/Chassis ECM Transmission/Chassis electronic control system Shift lever switch Transmission gear switch Transmission Output Speed (TOS) sensor Service/retarder brake switch Body up switch Transmission/Chassis ECM controlled systems (text) Transmission/Chassis ECM logged events (text) Steering system Steering tank and filters Steering pump Steering pump (low pressure standby) Steering pump (maximum flow) Steering valve Steering valve Hand Metering Unit (HMU) Secondary steering pump Steering system (sectional schematic) Steering system (ISO schematic) Hoist system model shot Hoist lever Hoist control position sensor Hoist, converter and brake tank Hydraulic tanks (rear) Hoist pump Hoist control valve (front) Hoist control valve (side) Hoist control valve (rear) Hoist control valve (hold) Hoist control valve (raise) Hoist control valve (lower) Hoist control valve (float) Hoist control valve (snub) Two-stage hoist cylinders Hoist hydraulic system (sectional schematic)

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SLIDE LIST 162. 163. 164. 165. 166. 167. 168. 169. 170. 171. 172. 173. 174. 175. 176. 177. 178. 179. 180. 181. 182. 183. 184. 185. 186. 187. 188. 189. 190. 191. 192. 193. 194. 195. 196. 197. 198.

Hoist hydraulic system (ISO schematic) Air and brake system model shot Oil cooled brake assembly (cutaway) Caliper disc brake assembly (cutaway) Front oil cooled brake assembly (cutaway) Air compressor Air dryer Service/retarder brake tanks Pressure protection valve Parking/secondary brake tank Air charging system Manual retarder valve Service brake valve Inverter valve (primary) Relay valves (caliper disc front brakes) Diverter valve cold oil solenoid Relay valves (oil cooled front brakes) Brake oil makeup tank Brake cylinder (rear) Brake cylinder (engaged) Slack adjuster (iron) Slack adjuster (released and engaged) Brake bleed screws Parking brake release valve Secondary steering pump Towing valve Brake release during towing Parking and secondary brake operation Service and retarder brake operation (caliper disc front brakes) Service and retarder brake operation (oil cooled front brakes) Brake oil cooling schematic (caliper disc front brakes) Brake oil cooling schematic (oil cooled front brakes) Brake oil cooler Brake cooling oil pressure taps Brake electronic control system Brake ECM (iron) Automatic Retarder Control (ARC) schematic

199. Engine Output Speed (EOS) sensor 200. ARC valve 201. Traction Control System (TCS) schematic 202. Wheel speed sensor 203. Traction Control System (TCS) valve 204. Traction Control System (TCS) operation (brakes released) 205. Traction Control System (TCS) operation (left brake engaged) 206. Model rear view

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INSTRUCTOR NOTES

SESV1721 01/00

Printed in U.S.A.