P076-end

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DIFFERENTIAL STEER COMPONENTS HYDRAULIC MOTOR INPUT

TRANSMISSION INPUT

TO LEFT FINAL DRIVE

TO RIGHT FINAL DRIVE

EQUALIZING PLANETARY

STEER DRIVE PLANETARY PLANETARY

62 DIFFERENTIAL STEER MECHANICAL OPERATION Differential steer tractors are not equipped with steering clutches but have a steering differential, a hydraulic pump, a hydraulic steering motor, and steering controls. • Steering differential has two power inputs: - Transmission - Hydraulic motor

The steering differential has two power inputs: a speed and direction (FORWARD and REVERSE) input from the transmission and a steering (LEFT and RIGHT) input from the hydraulic motor. The steering differential uses hydraulic motor power input to increase the speed of one track and equally decrease the speed of the other track. The resulting track speed difference turns the tractor.

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STMG 699 6/98 • Steering differential: - Steer planetary

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The steering differential consists of the steer planetary, the drive planetary, and the equalizing planetary. Color codes in this illustration designate the various components.

- Drive planetary - Equalizing planetary • Schematic color codes

The pinion, the bevel gear shaft, and the drive planetary carrier are red. The bevel gear shaft is splined to the drive planetary carrier. During turns, the pinion for the hydraulic motor drives the steer planetary ring gear. The hydraulic motor pinion and the steer planetary ring gear are orange. The center shaft connects the sun gears for all three planetaries. The sun gears and the center shaft are blue. The planet gears for all three planetaries are yellow. The center axle shaft is splined to the steer planetary and the equalizing planetary. Also, the steer planetary carrier is directly connected to the drive planetary ring gear. These components are green. The equalizing planetary ring gear is bolted to the right brake housing and remains stationary. The equalizing planetary is gray.

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DIFFERENTIAL STEER COMPONENTS STRAIGHT LINE OPERATION HYDRAULIC MOTOR INPUT

TRANSMISSION INPUT

TO LEFT FINAL DRIVE

TO RIGHT FINAL DRIVE

STEER PLANETARY

EQUALIZING PLANETARY

DRIVE PLANETARY

63 • Straight line operation - Steering motor does not turn - Transmission provides all power - Arrows show power flow - Outer axles rotate in same direction

This illustration shows the power flow through the differential steer system during straight line operation (FORWARD or REVERSE). In this condition, the hydraulic steering motor does not turn. Since the hydraulic steering motor does not turn, the steering pinion and steer planetary ring gear are stationary (gray) and the transmission provides all power flow through the system. The transmission sends power through the transfer gears, the pinion, the bevel gear, and the bevel gear shaft to the drive planetary carrier. At this point, the power divides causing a torque split. Most of the torque goes through the drive planetary ring gear to the steer planetary carrier. From the steer planetary carrier, the resulting power is transmitted to the left final drive through the left outer axle. The remaining torque from the drive planetary carrier is transmitted to the equalizing planetary sun gear through the drive planetary sun gear and the center axle.

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The equalizing planetary planet gears multiply the torque from the sun gear and send the resulting power through the right outer axle to the right final drive. The effect of this operation is that the left and right outer axles rotate in the same direction with the same power magnitude and the machine, therefore, tracks in a straight line.

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DIFFERENTIAL STEER COMPONENTS LEFT TURN - FORWARD HYDRAULIC MOTOR INPUT

TRANSMISSION INPUT

TO RIGHT FINAL DRIVE

TO LEFT FINAL DRIVE

STEER PLANETARY

DRIVE PLANETARY

EQUALIZING PLANETARY

64 • LEFT TURN FORWARD • Transmission input shown with black arrows • Steering motor input shown with white arrows

During a turn, both the transmission and the hydraulic motor provide inputs to the differential steer system with the transmission supplying most of the power to the system. The transmission input power is sent to the outer axles in the same manner as during straight line operation. The hydraulic motor input determines the turn direction and turn radius. The rpm of the hydraulic motor controls the turn radius (the higher the rpm, the smaller the turn radius) and the direction of rotation establishes the turn direction.

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During a LEFT TURN in the FORWARD direction, the hydraulic motor sends power through the steering planetary ring gear and the planet gears to the sun gear. • Steering motor input causes: - Right outer axle speed to increase - Left outer axle speed to decrease

The input from the hydraulic motor has two effects on the system: 1. The first effect is that the speed of all three sun gears and the speed of the center axle increases causing the speed of the right outer axle to increase. 2. The second effect is that the relative motion of the sun gear and planet gears in the steer and the drive planetaries cause the drive planetary ring gear, the steer planetary carrier, and the left outer axle to slow down. (This relative motion is due to the fact that the drive planetary carrier is turning at a constant rpm.) The speed decrease of the left outer axle is equal to the speed increase of the right outer axle.

• Reversing steering motor causes opposite turn

To make a RIGHT TURN, the direction of the hydraulic motor is opposite of the direction for a LEFT TURN. The motor now sends power to the steering planetary carrier causing an increase in the speed of the steering planetary carrier, the drive planetary ring gear, and the left outer axle. Simultaneously, all three sun gears, the center axle, and the right outer axle slow down. The speed decrease of the right outer axle is equal to the speed increase of the left outer axle. NOTE: During normal operation, this system does not provide a "pivot turn" capability. INSTRUCTOR NOTE: For more information about differential steering operation, see STMG 547 "D8N Track-type Tractor—Power Train and Implements" (Form SESV1547).

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STEERING COMPARISON - ONE PUMP vs TWO PUMPS FIRST SPEED FORWARD ONE PUMP WITH IMPLEMENTS 4.9 TO 6.0 M (16 TO 20 FT)*

ONE PUMP WITHOUT IMPLEMENTS 1.8 TO 2.3 M (5.9 TO 7.5 FT)* TWO PUMPS - WITH OR WITHOUT IMPLEMENTS 1.2 TO 1.8 M (3.9 TO 5.9 FT)* * INSIDE TURNING DIAMETER

65 • Two pump system provides tighter turn radius

This slide shows the advantage the two pump system has over the one pump system. The former system had a larger turning radius when the operator made a turn while using an implement. The two pump system provides the operator with a tighter turn radius with or without using the implements.

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D8R STEERING AND IMPLEMENT HYDRAULIC SYSTEM

STEERING MOTOR

STEERING SYSTEM

STEERING PUMP CHARGE PUMP

STEERING PILOT VALVE

BYPASS AND PRESSURE CONTROL GROUP

RIPPER CYLINDERS

STEERING CHARGE CIRCUIT FILTER

RIPPER DIVERTER VALVE TANK

IMPLEMENT SYSTEM IMPLEMENT PUMP INLET MANIFOLD RIPPER QUICK-DROP VALVE

LIFT TILT

LIFT CYLINDERS

TILT CYLINDER/S

END COVER

66

Differential Steering System • Steering and implement systems connected at two points: - Ripper diverter valve - Bypass and pressure control group • Single quick-drop valve • Color codes for schematics

This block diagram shows the steering and implement hydraulic system. The two systems are functionally separate, but they are connected at two points. Charge pressure is used to move the ripper diverter valve, and the implement pump output is sent to the bypass and pressure control group to supplement charge flow if the pressure decreases below a specified value. A single quick-drop valve is used for both lift cylinders. The various color codes which will be used in this section of the presentation to identify oil flow and pressures are: Red

- Drive loop or high pressure

Red and White Stripes

- First reduction of supply pressure

Red Dots

- Second reduction of supply pressure

Blue

- Blocked oil

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Orange

- Charge pressure

Orange and White Stripes

- Pilot pressure

Orange Dots

- Pump control pressure

Green

- Tank or case drain oil

Yellow

- Activated valve envelopes or moving parts

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1

2 4

3

67

• Pilot valve location • Contains two pressure reducing valves 1. Pilot pressure tap (right turn) 2. Pilot pressure tap (left turn) 3. Return hose 4. Charge pressure hose

The steering pump is controlled by a pilot valve connected to the bottom of the steering tiller. The valve contains two pressure reducing valves that convert charge pressure to pilot pressure. The two pressure taps are for the right (1) and left (2) steer pilot pressures. The hoses (3 and 4) are for the return oil and charge pressure, respectively.

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6

7

5 1 3

2 4

68

• Steering pump components: 1. Charge pump 2. Pressure compensator valve 3. Charge pressure relief 4. Right crossover relief valve 5. Left crossover relief valve 6. Pump control spool 7. Pump control piston and pressure taps

The steering pump circuit is a closed loop hydraulic system which includes an axial piston pump with over-center capability. The steering pump contains the charge pump (1), the pressure compensator (cutoff) valve (2), the charge pressure relief valve (3), and the right and left crossover relief and makeup valves (4 and 5). The charge pump (1) is contained in the end of the steering pump. The pump control spool (6) and the pump control piston (7) use charge pressure oil to move the swashplate for left and right turns. The pressure taps on the top of the pump control piston are for troubleshooting steering problems and adjusting the neutral setting of the steering pump.

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1 2 3

69

• Steering motor has flushing valve in port plate • Charge and case drain oil cool motor 1. Steering motor 2. Right steer pressure tap 3. Left steer pressure tap

The steering motor (1) is a bent axis design with a self-contained flushing valve in the port plate. The addition of this valve allows a controlled amount of oil from the low pressure side of the steering motor to flow into the motor case to cool, lubricate, and flush all components of the motor. Oil from the steering pump case (case drain oil) is sent to the bypass and pressure control valve and then to the steering motor to provide additional cooling. The combined oil flow in the motor is directed to the bypass and pressure control group and then sent to the tank. The top pressure tap (2) on the motor is for the right steer pressure and the bottom tap (3) is for the left steer pressure. When the operator moves the tiller lever to the right or left during a stall condition, system pressure will be approximately 40000 kPa (5800 psi) with the brakes applied.

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70

• Bypass and pressure control group (arrow)

The bypass and pressure control group (arrow) is a collection manifold for the charge pressure and cooling circuit of the steering system. The control valve group is mounted on the transmission case directly to the right of the steering motor.

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2 3

1

4

71

• Bypass and pressure control group: - Directs charge oil through filter and cooler - Protects circuit from high pressures - Directs implement oil to charge circuit for back-up

The bypass and pressure control group directs oil from the charge pump to the filter, the pressure control valve and then to the cooler. The oil then returns to the pressure control valve and enters the steering closed loop. The valve group also contains the cooler and cold oil bypass valves and controls the makeup functions for the steering charge pump oil circuit. The three pressure taps are: - Steering pump case drain (1) - Charge pump discharge pressure (2) - Charge pump relief pressure (3)

- Contains three pressure taps: 1. Steering pump case drain 2. Charge pump discharge pressure 3. Charge pump relief pressure 4. Check valve

The pilot and ripper diverter valve use charge oil from the upstream side of the cooler. This pressure is lower than the charge pump discharge pressure but higher than the charge pump relief pressure. The check valve (4) is used to block oil flow from the steering circuit into the implement circuit. If the steering system charge pressure decreases below 2000 kPa (290 psi), oil from the implement pump flows through the check valve to replenish the charge circuit.

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2 1

7 6

5

4

3

72

• Hydraulic tank for steering and implement systems: 1. Hydraulic tank 2. Case drain filter 3. Filter 4. Temperature switch 5. Bypass switch 6. Pressure tap 7. S•O•S tap

The hydraulic tank (1) serves as a reservoir for the steering and implement hydraulic oil. The hydraulic tank contains a 165 micron screen filter for the implement circuit, while the steering system return oil is filtered by the case drain reverse flow element (2). The return filter and the bypass valve, the fill strainer, the Electronic Monitoring System temperature switch, the oil level sight glass, the vacuum breaker relief valve, and the ecology drain are additional features of the tank. The tank holds 70 L (18.5 gal.) of oil which represents a 21% increase in oil capacity from the former model. The steering charge circuit oil filter (3) is located behind a hinged access door on the right side of the machine and in front of the tank. The filter has a spin-on canister, an oil pressure tap (6), an oil sampling port (7), a bypass switch (5), and a temperature override switch (4). If either system overheats, the Electronic Monitoring System will register a Category 3 Warning.

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73

• Hydraulic tank drain valve (arrow)

The drain plug for the hydraulic tank is located below the tank directly above the right track. To drain the oil, remove the cover (arrow) to access the ecology drain valve. Install a 25.4 mm (1 in.) pipe with 1 - 11 1/2 NPTF threads to unseat the valve (not shown) to start the flow of oil. To stop the flow of oil, remove the pipe and a spring will close the valve.

STMG 633 12/92

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1

2

74

1. Steering and implement cooler 2. Cooler pressure tap • Charge oil is filtered then cooled

The hydraulic oil cooler (1) is an air-to-oil design located on the front left side of the engine directly behind the radiator guard. The charge pump oil is filtered and sent through the cooler to the steering pump. The cooler has a heat rejection rating of 14 kW (13 Btu/sec.) at 57 Lpm (14.8 gpm) and dissipates the heat from the steering and implement systems. Located at the bottom of the cooler is the cooler pressure tap (2). The bypass and pressure control valve contains the cooler bypass relief valve. This valve is set to open and bypass charge pump oil around the cooler if the pressure differential is higher than 345 kPa (50 psi). The cooler is the same part number used in the previous model, but the system pressure is higher, approximately 2500 kPa (365 psi).

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STEERING MOTOR

STEERING PUMP

PILOT VALVE

BYPASS AND PRESSURE CONTROL GROUP

COOLER

TO RIPPER DIVERTER VALVE

TO CASE DRAIN FILTER IN TANK FROM IMPLEMENT PUMP CASE FROM IMPLEMENT PUMP SUPPLY

STEERING CHARGE CIRCUIT FILTER

D8R STEERING SYSTEM

75 Steering System Operation • Steering system with engine running and tiller in NEUTRAL

This schematic shows the components and conditions of the steering system with the engine started and the dual twist tiller in NEUTRAL (no turn). The major components of this system are: the steering pump, the steering motor, the pilot valve, the bypass and pressure control group, the steering charge circuit filter, and the cooler. Flow to the closed loop steering system is supplied by an axial piston pump with over-center capability. Components included in the pump are:

• Steering system components

Charge pump: Fills the system with oil during start-up and provides cool oil for the drive loops and steering pilot valve. This oil is called "charge pump discharge pressure" and is 345 to 550 kPa (50 to 80 psi) higher than charge pressure.

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Pressure compensator (cutoff) valve: When the pressure in either side of the loop reaches 40000 kPa (5800 psi), this valve destrokes the pump by draining the charge pressure sent to the pump control spool to move the pump control piston. Charge pressure relief valve: This valve limits the charge pressure to 2500 kPa (365 psi) after the charge pump oil is filtered and cooled. Charge oil is then sent to the drive loop, pilot valve, ripper diverter valve, and pump control piston. Crossover relief and makeup valves: Each side of the drive loop has a valve that limits the pressure spikes and also directs the charge pressure through the internal check valve to fill the low pressure side of the loop. Pump control spool and pump control piston: Oil pressure from the pilot valve moves the spool a small distance and directs charge pressure to either end of the pump control piston. As the pump control piston moves and changes the angle of the swashplate, the feedback link of the pump control spool follows up and maintains the correct pressure to the pump control piston for the amount of steering flow requested. In the NEUTRAL (or no turn) position, a small amount of pressure is present on both ends of the pump control piston. Other components included in the steering system are: Pilot valve: Contains two pressure reducing valves which control the displacement of the steering pump. Pressure from the pilot valve is set to begin upstroking the pump at 600 kPa (87 psi) and provide maximum displacement at 1800 kPa (261 psi). Steering motor with flushing valve: Uses flow from the steering pump to turn the motor clockwise or counterclockwise for either left or right turns. A flushing valve that meters oil from the low pressure side of the loop is contained in the port plate to help keep the motor cool during operation. Steering charge circuit filter: Spin-on filter housing with a bypass valve rated at 175 kPa (25 psi). The normally open bypass switch is installed in the inlet passage and held closed by the bypass valve. When the bypass valve opens to bypass oil flow around the filter element, the switch opens and the Electronic Monitoring System provides a Category 3 Warning. The alert indicator and action lamp flash and the action alarm sounds.

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Bypass and pressure control group: This valve group serves as a collection manifold for the charge pressure and cooling circuit of the steering system. The valve group directs oil from the charge pump, through the filter and the cooler, and then back to the steering pump. The bypass and pressure control group also provides the oil cooler bypass and makeup functions for the charge circuit. Components included in the bypass and pressure control group are: Cold oil bypass valve: This valve protects the charge circuit and opens at 3200 kPa (460 psi) when the oil is cold. Cooler bypass valve: This valve protects the cooler from differential pressures higher than 345 kPa (50 psi). Pressure reducing and check valve: If the charge pump pressure decreases below 2000 kPa (290 psi), oil from the implement pump flows through the check valve and the pressure reducing valve to replenish the charge circuit. Cooling orifice: As the case drain oil from the steering pump flows into the pressure control group, the flow is restricted and directed into the steering motor for additional cooling.

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D8R STEERING PILOT VALVE NO TURN

LEFT STEER LOOP PRESSURE

RIGHT STEER LOOP PRESSURE

TO PUMP CONTROL SPOOL

FROM BYPASS AND PRESSURE CONTROL GROUP

TO PUMP CONTROL SPOOL

76 • Pilot control valve sends signal to move swashplate • Feedback lever maintains desired pump flow

The pilot signal to the pump control spool originates at the pilot control valve. This valve contains two pressure reducing valves that use charge pressure for the source of oil. The pump swashplate angle is directly related to the amount of oil pressure sent from the pilot valve to the pump control spool. The pump control spool acts as a servo valve to direct charge pressure oil in and out of the pump control piston to mechanically move the swashplate. A feedback lever which connects the pump control piston to the pump control spool helps maintain pump flow for any given pilot signal.

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D8R STEERING PUMP NO TURN

RIGHT STEER LOOP

PUMP CONTROL PISTON PRESSURE RIGHT LOOP LEFT LOOP

TO STEER MOTOR (RIGHT)

CHARGE PUMP

CHARGE PRESSURE PRESSURE COMPENSATOR RELIEF VALVE CROSSOVER RELIEF VALVE

STEERING PUMP PUMP CONTROL PISTON

TO BYPASS AND PRESSURE CONTROL GROUP

TO STEER MOTOR (LEFT)

LEFT STEER LOOP PUMP CONTROL SPOOL

FROM BYPASS AND PRESSURE CONTROL VALVE TO BYPASS AND PRESSURE CONTROL VALVE

TO STEERING PILOT VALVE (RIGHT)

TO STEERING PILOT VALVE (LEFT)

77 • Charge pressure oil in pump goes to: - Charge pressure relief valve - Right and left crossover reliefs - Pressure compensator valve - Pump control spool - Pump control piston

This slide shows a close view of the steering pump in the NEUTRAL (no turn) condition. Charge pressure oil from the bypass and pressure control group enters the steering pump and flows to the charge pressure relief valve, the right and left crossover relief valves, and the pressure compensator valve. Charge oil also flows through the orifice to the pump control spool and pressurizes both ends of the pump control piston. After the pump control piston is pressurized, a drain passage in the pump control spool constantly bleeds a small amount of charge pressure oil to the tank. Most of the charge pressure oil flows to the tank through the charge pressure relief valve.

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D8R STEER MOTOR NO TURN FROM STEER PUMP

RIGHT STEER LOOP PRESSURE

FLUSHING VALVE

TO BYPASS AND PRESSURE CONTROL GROUP

FROM BYPASS AND PRESSURE CONTROL GROUP

FROM STEER PUMP LEFT STEER LOOP PRESSURE

78 • In NEUTRAL, flushing valve blocks charge oil • When turning, flushing valve lets return oil flow through motor • Additional source of cooling oil from pump case drain

In the NEUTRAL (no turn) condition, charge pressure is prevented from flowing through the steering motor because the flushing valve is centered. The flushing valve permits oil to flow from the low pressure side of the loop through the valve when a right or left turn is initiated. Two sources of cooling oil are provided to the motor: The first is the internal flushing valve in the port plate and the second is the steering pump case drain oil that is routed through the bypass and pressure control group to the motor. On many systems, a case drain pressure test for the steering motor is a good diagnostic check, but with the two sources of flow going through the motor, a pressure tap is not provided.

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STEERING MOTOR FLUSHING VALVE

PIN

79 • Flushing valve lets oil flow through motor during turns • Pump case drain oil sent to motor for more cooling

The flushing valve is contained within the port plate of the steering motor. This valve is designed to bleed off approximately 4 Lpm (1 gpm) of flow from the motor when the steer pressure increases to 2500 kPa (262 psi). When the pressure in the drive side of the loop is 2500 kPa (262 psi) higher than the return side, the higher pressure moves the pin and allows oil to flow through the port plate into the motor case. This oil combines with the steering pump case drain oil for more cooling. The combined flow is directed through the bypass and pressure control group to the tank. NOTE: Longitudinal slots are machined into the round pin in the port plate.

STMG 699 6/98

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D8R STEERING PILOT VALVE LEFT TURN

LEFT STEER LOOP PRESSURE

RIGHT STEER LOOP PRESSURE

FROM PUMP CONTROL SPOOL

FROM BYPASS AND PRESSURE CONTROL GROUP

TO PUMP CONTROL SPOOL

80 • LEFT TURN operation • Tiller moves right steering plunger • Pilot pressure moves pump control spool

This schematic shows the operation of the steering system when the operator moves the dual twist tiller for a LEFT TURN. The dual twist tiller moves linkage that causes the left steering plunger to retract and send pilot oil to the pump control spool in the steering pump. Pressure from the pilot valve is set to begin upstroking the pump at 600 kPa (87 psi) and provide maximum displacement at 1800 kPa (261 psi).

STMG 699 6/98

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D8R STEERING PUMP LEFT TURN PUMP CONTROL PISTON PRESSURE LEFT LOOP

TO STEER MOTOR (RIGHT)

CHARGE PUMP

RIGHT LOOP

CHARGE PRESSURE PRESSURE COMPENSATOR RELIEF VALVE

STEERING PUMP

CROSSOVER RELIEF VALVE

PUMP CONTROL PISTON

TO BYPASS AND PRESSURE CONTROL GROUP

TO STEER MOTOR (LEFT)

PUMP CONTROL SPOOL

FROM BYPASS AND PRESSURE CONTROL VALVE TO BYPASS AND PRESSURE CONTROL VALVE

TO STEERING PILOT VALVE (RIGHT)

FROM STEERING PILOT VALVE (LEFT)

81 • Oil from control spool to piston moves swashplate

• Crossover relief valves: - Limit pressure spikes - Provide makeup oil • Pressure compensator destrokes pump in stall condition

This slide shows the steering pump during a LEFT TURN. The pilot valve sends oil to the left end of the pump control spool which directs charge pressure oil to the pump control piston. The control piston mechanically moves the swashplate to the desired pump angle. Steering pump flow is then sent to the steering motor which provides a mechanical input to steer the machine. As the pressure increases in the drive side of the steer loop, the left crossover relief valve closes. The right crossover relief valve opens and lets charge pressure oil flow into the return side to provide makeup oil to replenish leakage in the loop. During a stall condition, the pressure spike which occurs in the drive side of the loop is relieved by the crossover relief valve and sent to the return side of the loop. If the operator continues to hold the tiller in the same position, the pressure compensator valve, which is set at 40000 kPa (5800 psi), opens and drains the oil sent by the pump control spool to the pump control piston. The piston causes the swashplate to move toward a minimum angle and maintain maximum pressure.

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NOTE: Charge pressure (orange) and low pressure return oil (red and white stripes) are equal. The respective flows are shown this way to help keep the circuits separate.

STMG 699 6/98

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STEERING PUMP END VIEW

RIGHT CROSSOVER RELIEF VALVE

TOP

CHARGE PRESSURE RELIEF VALVE

ORIFICE PLUG

LEFT CROSSOVER RELIEF VALVE

PRESSURE COMPENSATOR VALVE

82 • Pump shown in LEFT TURN condition • Four relief valves

This slide shows the steering pump during a LEFT TURN. The left crossover relief valve is closed, and the drive loop pressure (red) is sent to the steering motor. The right crossover relief valve is in the makeup mode, allowing charge pressure oil (orange) to replenish the return side of the loop. If a pressure spike occurs in the drive side of the loop, the left crossover relief valve opens and directs excess oil into the return side of the loop. The pressure compensator valve destrokes the pump if the pressure exceeds the valve setting by draining the charge pressure oil (orange) that is sent to the pump control spool and the pump control piston. The orifice plug just above the left crossover relief valve helps maintain the charge pressure when the pressure compensator drains the charge oil to the pump control spool and the pump control piston. The charge pressure relief valve limits the charge pressure (orange) used in the steering system and continually drains the excess oil that is not required in any of the circuits.

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D8R STEER MOTOR LEFT TURN TO STEER PUMP

RIGHT STEER LOOP PRESSURE

FLUSHING VALVE

TO BYPASS AND PRESSURE CONTROL GROUP

FROM STEER PUMP FROM BYPASS AND PRESSURE CONTROL GROUP

LEFT STEER LOOP PRESSURE

83 • High pressure oil rotates motor during turns • Flushing valve sends return oil through motor

The high pressure oil sent to the steering motor causes the motor to rotate and provide a mechanical input to the steer planetary in the bevel gear case. The high pressure oil moves the flushing valve. When the valve moves, low pressure (return) oil flows into the motor housing and then to the bypass and pressure control group.

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STEERING PUMP (TOP VIEW) LEFT TURN SPRING COLLAR

RETAINER

FROM PILOT VALVE RIGHT SIDE PUMP CONTROL SPOOL

ROD

RIGHT LEVER ARM STOP

COMPRESSION SPRING

LEFT LEVER ARM

PUMP CONTROL PISTON LEFT SIDE

FEEDBACK LEVER

TO PILOT VALVE PIVOT POINT

SPOOL CONTROL ARM

84 • Feedback lever connects control spool to piston • Control spool moves control piston • Control spool movement very small • Pilot valve sends oil to control spool • Control spool directs charge oil to piston

The pump control spool uses pilot oil (orange and white stripes) to control the amount of charge pressure oil (orange dots) that is sent to the pump control piston. The movement of the pump control spool is approximately 2.00 mm (.078 in.) in each direction. This spool constantly meters the charge oil to maintain the correct pressure at the pump control piston and the correct swashplate angle. This slide shows the pilot valve moved to the LEFT TURN position. Pilot pressure is proportional to the amount of lever movement that is directed to the upper end of the pump control spool. As the spool moves down, a passage opens and sends charge pressure oil to the upper end of the pump control piston. At the same time, the spool control arm shifts the left lever arm. This movement increases the tension of the compression spring proportional to the force created by the pilot oil from the pilot valve. The lever arms and the feedback lever pivot on the eccentric screw (pivot point). An adjustment screw can be used to adjust the center position of the spool.

➥

STMG 699 6/98

• Charge oil moves control piston

• Feedback lever moves control spool toward neutral

• During stall, swashplate moves toward minimum angle • System pressure maintained by compensator valve

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Charge pressure oil directed to the upper end of the pump control piston compresses the large springs and moves the pump control piston down. As the pump control piston moves, the feedback lever pivots at the pivot point and the stop on the feedback lever opens the right lever arm to cause more compression on the spring. The spring force moves the spool back toward the neutral position. As the spool moves toward neutral, the opening to the passage for charge pressure oil to the pump control piston is reduced. The charge pressure at the upper end of the piston is decreased and the large springs move the swashplate toward minimum angle to maintain the turn. If the operator stalls the steer motor, the pressure compensator valve destrokes the pump by bleeding off charge pressure oil at the pump control piston. The large springs in the pump control piston move the swashplate toward minimum angle to reduce pump output. This condition occurs automatically and prevents the operator from stalling the steering system at maximum flow. If the operator holds the tiller at the full left turn position with the brakes engaged, the crossover relief valve will limit the pressure spike and the pressure compensator will bleed the charge pressure oil from the upper end of the control piston to decrease the angle of the swashplate. Pump flow is at minimum, but the system pressure is at the setting of the pressure compensator. NOTE: In NEUTRAL (no turn), the pump control spool (if centered) will send equal pressure to each end of the pump control piston. Since 600 kPa (87 psi) is needed to move the pump control piston, a difference of more that 600 kPa (87 psi) will cause the machine to move when the parking brake lever is moved to the released position. The adjustment screws on the pump control spool are used to adjust the pressures on each end of the pump control piston. If the spool needs adjustment, follow the procedure in the Service Module Supplement (Form SENR4983). Loosening and tightening the locknuts will change the center position of the pump control spool. The small adjustment screws on both ends of the pump control piston are not adjustable and have factory installed tamper proof caps. Any attempt to adjust the screws will cause the valve to react differently to pilot oil directed from the tiller lever. Replace the valve if the caps have been tampered with and if the valve is damaged.

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PUMP CONTROL PISTON

FEEDBACK LEVER

PUMP CONTROL VALVE

RIGHT CROSSOVER RELIEF VALVE

STEERING PUMP SIDE VIEW

CHARGE PUMP

SWASHPLATE

PISTONS

LEFT CROSSOVER RELIEF VALVE

85 • Steering pump components: - Right and left crossover relief valves - Charge pump - Pump control valve - Feedback lever - Pump control piston - Swashplate - Pistons

This slide shows a side view of the steering pump. The following components are visible: the right and left crossover relief valves, the charge pump, the pump control valve, the feedback lever, the pump control piston, the swashplate, and the pistons.

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BYPASS AND PRESSURE CONTROL GROUP

TO STEER MOTOR CASE DRAIN

TO COOLER, PILOT, AND FROM RIPPER DIVERTER VALVE STEER PUMP CHARGE FROM FROM PUMP CHARGE CASE DRAIN DISCHARGE CHARGE PUMP PUMP RELIEF COOLER PRESSURE PRESSURE

CASE RETURN PRESSURE COLD OIL BYPASS

COOLING ORIFICE FROM STEER MOTOR CASE DRAIN

CHARGE CIRCUIT MAKEUP VALVE

COOLER BYPASS

TO CASE DRAIN FILTER IN TANK TO FILTER FROM IMPLEMENT PUMP CASE DRAIN

FROM FILTER

TO CHARGE PRESSURE RELIEF VALVE

FROM IMPLEMENT PUMP SUPPLY

86 • Bypass and pressure control group directs oil through filter and cooler

• Filter and cooler have cold oil bypass valves

• Implement pump assists steering charge circuit • Cooling orifice sends steering pump case drain oil to motor

The main purpose of the bypass and pressure control group is to direct charge pump discharge oil through the steering charge circuit filter and cooler. After the oil has been filtered and before it is cooled, the charge pressure oil is available for the ripper diverter valve and steering pilot valve. After the oil goes through the cooler, the flow is directed to the steering pump control spool and to the drive loop for makeup oil. The cold oil bypass valve protects the filter and charge pump during startup and the cooler bypass valve protects the cooler. The cold oil bypass valve is set to open at 3200 kPa (460 psi). The cooler bypass valve will open when the pressure differential is 345 kPa (50 psi). The charge circuit makeup valve is a pressure reducing valve that directs implement pump oil to the charge circuit if the charge pressure decreases below 2000 kPa (290 psi). The cooling orifice restricts the flow of steering pump case drain oil. This restriction forces some of the steering pump case drain oil through a line to the steering motor case. This oil adds to the oil from the steering motor flushing valve for cooling and lubrication of the steering motor.

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2

3

10

9

6

4 7

1

5 8

87

• Component locations: 1. Front idler 2. Front roller frame 3. Rear roller frame 4. Pivot shaft 5. Rear idler 6. Track 7. Major bogies 8. Minor bogies 9. Cover plate 10. Guide cover • Sealed and lubricated track • Balanced design

UNDERCARRIAGE The D8R suspended undercarriage is designed to absorb impact loads to reduce the shock loads transferred to the machine frame. Two types of undercarriage are available: a suspended undercarriage (shown) that provides up to 15% more ground contact and a non-suspended undercarriage for applications involving moderate impact or highly abrasive materials. The main components of the undercarriage are: the front idler (1), the front roller frame (2), the rear roller frame (3), the pivot shaft (4), the rear idler (5), the track (6), the major bogies (7), the minor bogies (8), the cover plate (9) for the track adjuster, and the cover (10) for the guides. The pivot shaft connects the right and left rear roller frames and transmits the ground shocks directly to the main frame rather than through the power train components. The roller frames can oscillate around the pivot shaft. The equalizer bar (not shown) is an additional component of the undercarriage. The equalizer bar is pinned in the center of the tractor and can rotate around the center pin joint. The equalizer bar connects the two rear track roller frames and controls the degree that the roller frames can oscillate around the pivot shaft.

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• Track tension is adjustable

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The front roller frame slides inside the rear roller frame. Pumping grease into a cylinder inside the rear roller frame increases the recoil spring tension. A key and slot mechanism in the front and rear track roller frames allows the front roller frame to slide in and out of the rear roller frame, but prevents the front roller frame from rotating inside the rear. To increase track tension, remove the adjusting valve cover plate (9) and add grease through the adjusting valve. To decrease track tension, loosen the relief valve and allow grease to escape. Then, close the relief valve and add additional grease through the adjusting valve. NOTE: The D8R Operation and Maintenance Manual (Form SEBU6891) shows the correct track adjustment procedure.

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88

• Pivot shaft dipstick (arrow)

The pivot shaft oil can be checked by removing the dipstick (arrow) from the container in the compartment just behind the batteries. The oil level should be maintained to the FULL mark.

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1

2

3

89

• Equalizer bar end pin components: 1. Grease fitting 2. Relief valves 3. Limited slip seals

This slide shows the location of the equalizer bar end pin grease fitting (1). Using a hand operated grease gun filled with 80w90 EP gear oil, fill the joint through the grease fitting until the oil flows from the relief valves (2). The joint can be filled with 5P0960 Multipurpose Molybdenum Grease (MPGM) if current maintenance practices make filling with EP oil difficult. The joint is filled at the factory with EP oil due to its greater load carrying capabilities and lubricating qualities. The combination of EP oil and MPGM grease will not be detrimental. The equalizer bar has limited slip end pin seals (3). NOTE: The D8N can be modified to accept these improvements if the machine is updated to reduce oscillation, and the equalizer bar is modified to provide pressure relief during the grease fill.

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D8R STEERING AND IMPLEMENT HYDRAULIC SYSTEM

STEERING MOTOR

STEERING SYSTEM

STEERING PUMP CHARGE PUMP

STEERING PILOT VALVE

BYPASS AND PRESSURE CONTROL GROUP

RIPPER CYLINDERS

RIPPER DIVERTER VALVE

STEERING CHARGE CIRCUIT FILTER

TANK

IMPLEMENT SYSTEM IMPLEMENT PUMP INLET MANIFOLD RIPPER QUICK-DROP VALVE

LIFT TILT

LIFT CYLINDERS

TILT CYLINDER

END COVER

90 IMPLEMENT HYDRAULIC SYSTEM • Implement hydraulic system components: - Pump - Three control valves with inlet manifold - Single quick-drop valve - Ripper diverter valve • Two systems share two functions

The implement hydraulic system consists of a variable displacement pump, three control valves with an inlet manifold, and a single quick-drop valve. The steering and implement systems are connected at one point. The implement pump output is sent to the bypass and pressure control group to supplement the steering charge pump if the discharge pressure decreases below a specified value.

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1

2

3

91

• Hydraulic tank components: 1. Cap and fill tube 2. Vacuum breaker/relief valve 3. Sight gauge

The hydraulic tank serves as a reservoir for the implement and steering hydraulic oil and is located on the right fender. The oil cap and fill tube (1) are located on the top of the tank. Inside the fill tube is a fine mesh screen which removes large particles of dirt or foreign material from the oil as the tank is filled. A vacuum breaker/relief valve (2) is also located on the top of the tank. The oil level sight gauge (3) on the front of the tank permits an easy check of the hydraulic system oil level. Always clean the sight gauge to be sure the oil level is visible. Dirt and stains on the glass frequently give the appearance of a full tank.

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1

2

3

92

• Implement hydraulic system components: 1. Implement pump 2. Flow compensator valve 3. Pressure compensator valve

The implement hydraulic system is load sensing and pressure compensated with a variable displacement slipper-type pump (1). The pump is very similar to many other models in the Caterpillar equipment line. Mounted on the left side of the pump are the flow compensator valve (2) and the pressure compensator valve (3). The implement hydraulic pump maintains a low standby pressure between 2100 kPa (305 psi) and 3600 kPa (520 psi). Margin pressure is 2100 kPa (305 psi) and high pressure cutoff is 26200 kPa (3800 psi). Contained in the inlet manifold of the implement valve stack are the main relief valve and the charging valve. The main relief valve protects the system from pressure spikes over 27000 kPa (3900 psi). The charging valve restricts return flow to the tank that helps prevent cavitation in the cylinders.

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1 2 5 3

4

93

• Implement stack includes: ripper, lift, and tilt valves • Ripper control valve standard 1. Signal oil pressure tap 2. Pump discharge pressure tap 3. Main relief valve 4. Charging valve 5. Supply line to steer circuit • Charging valve assists makeup and quick-drop valve • Supply line sends implement oil to steering charge circuit

The implement control valve consists of three parallel valve sections: ripper, dozer lift, and dozer tilt. The ripper control valve is standard on all machines even if the machine is purchased without a ripper. The ripper hardware may be added in the future along with the ripper diverter valve. Pressure taps are provided on the inlet manifold for signal oil (1) and pump discharge (2). By using these pressure taps, margin pressure, low pressure standby and high pressure stall can be tested. The inlet manifold includes the main relief valve (3) and the return oil charging valve (4). The main relief valve is set at 27000 kPa (3900 psi), which is 2750 kPa (400 psi) higher than the pressure compensator (cutoff) valve. The main purpose of the main relief in the system is to eliminate pressure spikes. If the system is in a stall condition, the pressure cutoff valve will cause the implement pump to destroke toward a minimum angle. The charging valve restricts the cylinder return oil flow to the tank. This valve keeps oil pressure in the cylinder return oil passage of the implement control valves and is used with the makeup valves to prevent cavitation in the cylinders. A typical function when the charging valve assists the makeup valve and the quick-drop valve for the lift cylinders is when the dozer control lever is moved to the full lower position (quickdrop) and the dozer is lowered rapidly.

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The supply line (5) goes to the bypass and pressure control group and connects to the external check valve. This line supplies implement pump oil to the internal pressure reducing valve in the valve group. The pressure reducing valve in the bypass and pressure control valve provides implement pump oil to supplement the steering charge pump discharge oil if the charge pressure decreases below 2000 kPa (290 psi). Implement system pressure will be felt in this line at all times. NOTE: To connect the 1U5796 Differential Pressure Gauge Group to these two pressure taps, remove only the floor plate in the operator's station. Both hydraulic hose couplings can be connected to the pressure taps by laying down on the outside of the right side of the operator's station and using the right hand to secure them. The operator's seat and seat plate need not be removed for this test.

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2

1

94

• Implement hydraulic system components: 1. Threaded gland cylinders 2. Quick-drop valve

The threaded gland lift cylinders (1) have built-in bypass plungers that prevent high pressure loads at either end of the stroke. The single quick-drop valve (2) replaces the former quick-drop valves which were located on the head end of each lift cylinder.

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95

• Blade tilt cylinders (arrows)

The D8R is available with single or dual tilt cylinders (arrows). If the machine is equipped with a single cylinder, the left cylinder is replaced with a brace. The tilt control valve will operate either the single or dual tilt cylinder arrangement. The dozer tilt cylinders have the conventional bolt-on head design.

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2 6

1

5 4 3

96

• Ripper component locations: 1. Carriage 2. Shank and tooth 3. Ripper frame

This view of the rear of the machine shows the main components of a single shank ripper. The visible components include: the carriage (1), the shank and tooth assembly (2), the ripper frame (3), the lift cylinders (4), the tip cylinders (5), and the diverter valve (6). NOTE: The ripper shank and tooth assembly is mounted in the machine travel position. For the ripper to be used, the shank must be mounted in the carriage with the tooth pointing toward the ground.

4. Lift cylinders 5. Tip cylinders 6. Diverter valve

The machine can also be equipped with a multi-shank ripper for other ripping applications.

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3

1

2

4 5

97 • Ripper component locations: 1. Diverter valve switch 2. Ripper diverter valve 3. Pin puller toggle switch 4. Pin puller control valve 5. Pin puller cylinder

The optional ripper diverter valve group (2) is mounted on the rear of the machine. The control lever has been redesigned to accommodate the diverter valve switch (1). When the switch is depressed and the lever is moved left and right, the ripper tip will move in or out. Releasing the switch and moving the lever left and right will raise or lower the ripper. The switch activates a solenoid on the ripper diverter valve that sends steering system charge pressure oil to move the spool in the diverter valve. The diverter valve permits a single ripper control valve to be used for both operations. The single shank ripper can be equipped with an optional hydraulically operated pin puller (5). The pin puller control valve (4) allows the operator to release and engage the pin for the ripper shank with the toggle switch (3) without leaving the operator's station. Oil for operation of the pin puller circuit is supplied by the power train hydraulic system.

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D8R IMPLEMENT HYDRAULIC SYSTEM BYPASS AND PRESSURE CONTROL GROUP

STEERING CHARGE PRESSURE

INLET MANIFOLD RIPPER

DIVERTER

PUMP

LIFT TILT END COVER QUICK-DROP

98 Implement System Operation This diagram shows the hydraulic system with all the implements in HOLD. Oil is sent from the common steering and implement hydraulic tank to the variable displacement, piston-type pump. Supply oil is directed to the closed-center control valves. Return oil and pump case drain oil are sent to the tank. When a control lever is moved, oil from the implement control valve is directed to double acting implement cylinders. • Signal network in series • Highest signal pressure sent to pump control valve

The signal network line (orange) is in series with each control valve and passes through each valve body. The signal network terminates at the pump control valve. When an implement is activated, a signal is generated by the work port load. This signal is sent through the signal network. A resolver network inside the implement valves consists of a series of check valves which compare the signals from the implements and send the highest signal to the pump control valve.

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STEERING CHARGE PRESSURE

D8R IMPLEMENT HYDRAULIC SYSTEM TO BYPASS AND PRESSURE CONTROL VALVE

RIPPER DIVERTER TO BYPASS AND PRESSURE CONTROL VALVE

TO STEERING CHARGE PUMP

X

INLET MANIFOLD

IMPLEMENT PUMP

QUICK-DROP VALVE RIPPER

LIFT

TILT

TANK

99 • Schematic shows components in HOLD

This schematic shows the components and conditions in the implement system with the engine started and the implements in HOLD. The major components in this system are: the implement pump, the inlet manifold, the ripper, lift and tilt control valves, the quick-drop valve, and the ripper diverter valve.

• Three changes include: - Single quick-drop - Ripper diverter valve - Flow control spools are solid

Three changes have occurred from the D8N: a single quick-drop valve, an electrically actuated ripper diverter valve, and the flow control spool in the control valve is solid rather than hollow. In addition to the implement oil being used to move the cylinders, it also is sent to the bypass and pressure control group to supplement the charge pump if the discharge pressure decreases below 2000 kPa (290 psi). The ripper diverter valve uses steering charge pressure to move the ripper diverter spool when the operator selects the RIPPER TIP or LIFT functions.

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PRESSURE AND FLOW COMPENSATOR VALVE ADJUSTMENT SCREWS

PRESSURE COMPENSATOR (CUTOFF) SPRING

FLOW COMPENSATOR (MARGIN) SPRING

TO TANK

TO ACTUATOR PISTON FLOW COMPENSATOR (MARGIN) SPOOL

FROM OUTPUT PORT PRESSURE COMPENSATOR (CUTOFF) SPOOL

100 Implement Pump • Two spools in pump control valve: 1. Flow compensator 2. Pressure compensator

Shown here is the pressure compensator valve used on the implement pump. Two spools are installed in the valve: 1. The flow compensator (or margin) spool is on the left. This valve controls margin pressure and low pressure standby. Margin pressure is set at 2100 kPa (305 psi) above the signal pressure. Low pressure standby is approximately 3000 kPa (435 psi). If this pressure is below 2100 kPa (305 psi) or above 3600 kPa (520 psi), margin pressure should be checked. Adjusting the margin pressure to specification allows the standby pressure to be maintained within specification. 2. The pressure compensator (or cutoff) spool (on the right) controls the stall pressure. The valve is set at 24100 kPa (3500 psi). NOTE: Each spring has an individual adjustment screw.

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PUMP AND COMPENSATOR OPERATION ENGINE OFF

NO SIGNAL

PUMP OUTPUT LARGE ACTUATOR

YOKE PAD SWASHPLATE

DRIVE SHAFT

FLOW COMPENSATOR ( MARGIN) SPOOL

PRESSURE COMPENSATOR (CUTOFF) SPOOL

SMALL ACTUATOR AND BIAS SPRING PISTON AND BARREL ASSEMBLY

101 • Identify all labeled components

When the engine is OFF, the bias spring holds the swashplate at maximum angle.

• Bias spring holds swashplate at maximum angle

When the engine is started, the pump drive shaft starts to rotate. Oil is drawn into the piston bores. As the piston and barrel assembly rotates, the oil is forced out into the system.

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PUMP AND COMPENSATOR OPERATION LOW PRESSURE STANDBY NO SIGNAL

PUMP OUTPUT

102 • Pump produces flow: - Flow blocked at implement valves - Pressure increases - Margin spool moves up - Flow directed to large actuator - Pump is destroked

When no flow is demanded from the implements, no signal pressure is generated. System pressure (red and white stripes) generated by the pump is called "low pressure standby." The pump produces enough flow to compensate for system leakage at sufficient pressure to provide for instantaneous implement response when an implement is actuated. At machine start-up, the bias spring holds the swashplate at maximum angle. As the pump produces flow, system pressure begins to increase because the flow is blocked at the implement control valves. This pressure is felt under both the margin spool and the pressure cutoff spool. The margin spool moves up against the low spring force and permits system oil to go to the large actuator piston in the pump.

• Low pressure standby: - No flow demand - Minimum flow produced

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• Low pressure standby higher than margin

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As pressure in the large actuator piston increases, the large actuator piston overcomes the force of the bias spring and the pressure in the small actuator piston and moves the swashplate to a reduced angle. The large actuator piston moves to the right until the cross-drilled passage in the stem is uncovered. Oil in the large actuator piston then bleeds off to the pump case. At this minimum angle, the pump will produce just enough flow to make up for system leakage. The system pressure at this time is called "low pressure standby" and is approximately 3000 kPa (435 psi). Low pressure standby is higher than margin pressure. This characteristic is due to a higher back pressure created by the oil which is blocked at the closed-center valves when all the valves are in HOLD. Pump supply oil pushes the margin spool up and further compresses the margin spring. More supply oil then goes to the large control piston and flows through the cross-drilled hole in the stem to the pump case.

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PUMP AND COMPENSATOR OPERATION UPSTROKING SIGNAL

PUMP OUTPUT REDUCED PRESSURE

103 • Upstroking: - When flow is required - Signal is sent - Margin spool moves down - Drains large actuator - Bias spring and small actuator increase swashplate angle

When an implement requires flow, a signal is sent to the pump control valve. This signal causes the force (margin spring plus signal pressure) at the top of the margin spool to become higher than the supply pressure at the bottom of the spool. The spool then moves down, blocks oil to the large actuator piston and opens a passage to drain. Pressure at the large actuator piston is reduced or eliminated, which allows the bias spring to move the swashplate to an increased angle. The pump will now produce more flow. This condition is called "upstroking." The following conditions can result in upstroking the pump: 1. An implement control valve is activated when the system is at low pressure standby. 2. The control valve directional spool is moved for additional flow. 3. An additional circuit is activated.

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4. Engine rpm decreases. In this case, pump speed decreases which causes a decrease in flow and pump supply pressure. The pump must then upstroke to maintain the system flow requirements. NOTE: Signal pressure does not necessarily have to increase for the pump to upstroke. For example, if one implement is activated and is operating at 13800 kPa (2000 psi), the system supply pressure is 15900 kPa (2305 psi) due to the maximum signal pressure of 13800 kPa (2000 psi) plus the margin spring force. Now, if the operator activates another implement at an initial operating pressure of 6900 kPa (1000 psi), the maximum signal pressure is still 13800 kPa (2000 psi), but the supply pressure decreases momentarily to provide the increased flow now needed at the implements. The force at the top of the margin spool (now higher than the force at the bottom of the margin spool) pushes the spool down and allows oil in the pump control to drain. The swashplate angle increases and the pump provides more flow.

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PUMP AND COMPENSATOR OPERATION CONSTANT FLOW SIGNAL

PUMP OUTPUT REDUCED PRESSURE

104

- Signal pressure plus spring equals system pressure

As pump flow increases, pump supply pressure also increases. When the pump supply pressure (red) increases and equals the sum of the load pressure plus the margin spring pressure, the margin spool moves to a metering position and the system becomes stabilized.

- Swashplate at constant angle

The difference between the signal pressure and the pump supply pressure is the value of the margin spring, which is 2100 kPa (305 psi).

• Constant flow:

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PUMP AND COMPENSATOR OPERATION DESTROKING SIGNAL

PUMP OUTPUT

INCREASED PRESSURE

105 • Destroking: - Less flow required - System pressure moves margin spool up - Oil flows to large actuator - Swashplate angle is reduced • Four conditions for destroking

When less flow is needed, the pump is destroked. The pump destrokes when the force at the bottom of the margin spool becomes higher than at the top. The margin spool then moves up and allows more flow to the large actuator piston. Pressure in the large actuator piston then overcomes the combined force of the small actuator piston and bias spring and moves the swashplate to a reduced angle. The pump will now produce less flow. The following conditions can result in destroking the pump: 1. All implement control valves are moved to the HOLD position. The pump returns to low pressure standby. 2. The control valve directional stem is moved to reduce flow. 3. An additional circuit is deactivated. 4. Engine rpm increases. In this case, pump speed increases causing an increase in flow. The pump destrokes to maintain system flow requirements.

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• Pump flow stabilizes when margin spool moves to metering position

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As pump flow decreases, pump supply pressure also decreases. When the pump supply pressure (red) decreases and becomes the sum of load pressure plus margin pressure, the margin spool moves to a metering position and the system stabilizes. NOTE: Signal pressure does not necessarily have to decrease for the pump to destroke. For example, if two implements are activated with one at 13800 kPa (2000 psi) and the other at 6900 kPa (1000 psi), the system supply pressure is 15900 kPa (2305 psi) due to the maximum signal pressure of 13800 kPa (2000 psi) plus the margin spring force. Now, if the operator returns the implement at 6900 kPa (1000 psi) to HOLD, maximum signal pressure is still 13800 kPa (2000 psi), but the supply pressure increases due to reduced flow needed at the implements. The supply pressure will push the margin spring up and allow more oil to go to the pump control which causes the pump to destroke.

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PUMP AND COMPENSATOR OPERATION HIGH PRESSURE STALL SIGNAL AT MAX. PRESSURE

PUMP OUTPUT AT MAX. PRESSURE

106 • High pressure stall: - Margin spool is down - Pressure compensator is up - Flow directed to large actuator - Pump is destroked - System pressure at maximum

The pressure compensator (or cutoff) spool is in parallel with the flow compensator (or margin) spool. The pressure compensator limits the maximum system pressure at any given pump displacement. The spool is held down during normal operation by the pressure compensator spring. During stall or when system pressure is maximum, signal pressure is equal to pump supply pressure. The combination of the signal pressure and the margin spring forces the margin spool down. This movement of the margin spool normally opens a passage in the pump control valve for the oil in the large actuator piston to drain and causes the pump to upstroke. However, if the supply pressure is high enough, the pressure cutoff spool is forced up against the spring. This movement of the pressure cutoff spool blocks the oil in the large actuator piston from going to drain and allows supply oil to go to the large actuator piston. The increase in pressure allows the large actuator piston to overcome the combined force of the small actuator piston and bias spring to destroke the pump. The pump is now at minimum flow and pump supply pressure is at maximum. This condition is maintained for a single implement in a stall condition.

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• Main relief valve limits pressure spikes • Pressure cutoff spool destrokes pump

• Pump can still produce flow for other implements • Upstrokes to meet flow requirements

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This system also incorporates a main relief valve located in the inlet manifold. The pressure cutoff spool can be adjusted in the machine to destroke the pump at 24100 kPa (3500 psi). The main relief valve must be removed from the machine and adjusted to 27000 kPa (3900 psi) using the 1U5216 Test Block Manifold. This valve is set higher to limit pressure spikes in the system. When operating two or more implements with one in stall, the pump will produce flow to meet the needs of the other implements operating at a lower work port pressure. In this case, the pump could be producing up to maximum flow while the supply pressure is at the maximum of 24100 kPa (3500 psi). NOTE: Contained within the pump is a case drain relief valve. If the internal pressure exceeds 170 kPa (25 psi), excess flow will be directed to the inlet of the pump. The relief valve is designed to protect the pump shaft seals.

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D8R IMPLEMENT VALVES TO BYPASS AND PRESSURE CONTROL GROUP

IMPLEMENT PUMP PRESSURE

IMPLEMENT PUMP SIGNAL PRESSURE

SIGNAL LINE TO IMPLEMENT PUMP

INLET MANIFOLD

CHARGE RELIEF VALVE

SYSTEM RELIEF VALVE

TO IMPLEMENT PUMP SUPPLY

. FLOW CONTROL VALVE RIPPER TO RIPPER LIFT CYLINDERS FLOW CONTROL VALVE LIFT TO LIFT CYLINDERS FLOW CONTROL VALVE TILT

TO TILT CYLINDERS

107 Implement Control Valves • Signal line to pump compensator valve

The implement valve group consists of an inlet manifold, the ripper, lift, and tilt control valves and an end cover. All machines are equipped with this valve group. Even though the customer may not order the ripper, the valve is included in the stack.

• Oil sent to bypass and pressure control group

The signal line is connected from the inlet manifold to the pump compensator valve. Another line from the inlet manifold sends implement pump oil to the bypass and pressure control group in the steering system.

• Inlet manifold components:

The inlet manifold contains a system relief valve and a charge relief valve. The system relief valve limits pressure spikes and is set higher than the pressure compensator spool. The charge relief valve restricts return oil going to the tank when the pump is not upstroked. This restriction keeps oil pressure in the cylinder return oil passage of the implement control valves. This oil pressure can be used with the makeup valves to prevent cylinder cavitation.

- System relief valve - Charge relief valve

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DOZER LIFT VALVE HOLD PLUG

ROD END

HEAD END

RETURN TO TANK

FROM PREVIOUS VALVE

MAKEUP VALVE

MAIN CONTROL SPOOL

RESOLVER

LOAD CHECK VALVE FROM PUMP

FLOW CONTROL SPOOL

TO COMPENSATOR VALVE

108 • Control valve operation - Dozer lift valve

• Lift valve in HOLD • Axial passage open to tank • Flow control valve is initially to left • Flow blocked at control spool and pressure increases

The dozer lift valve is the second valve in the stack. The lift control valve is a closed-center, manually operated valve controlled through mechanical linkage. The lift valve has four positions: RAISE, HOLD, LOWER, and FLOAT. A centering spring keeps the spool in the HOLD position when the blade lift cylinders are not in use. To operate in the FLOAT condition, the operator must move the control lever forward until the detent balls hold the valve spool. The operator must manually release the lift control lever from the FLOAT position. This slide shows the lift control valve in HOLD. In HOLD, the center axial passage is open to the tank through a drain passage in the valve body. With the engine not running, the spring behind the flow control spool holds the flow control spool to the left. When the operator starts the machine, the pump sends oil through the inlet manifold to the flow control spool, out the throttling slots on the left side of the spool, through the load check valve, and to the main control spool. With the control spool in the HOLD position, oil cannot flow to the cylinders, and oil pressure will begin to increase.

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STMG 699 6/98 • Flow control spool moves to the right • Throttling slot on right closes • Throttling slot on left opens • Flow control spool maintains maximum pressure differential

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The increasing pressure in the chamber to the right of the load check valve pushes the flow control spool to the right against the force of the spring. Moving the flow control spool to the right closes the throttling slot on the left side of the spool. Oil can continue to flow to the remaining control valves in the system. In HOLD, pressure at the main control spool is equal to the flow control spool spring. Flow control spool: Receives all the oil flow from the inlet valve group. The flow control spool provides the "pressure compensating" feature of the lift circuit by controlling the maximum pressure drop across the lift control spool. This operation results in a constant implement speed for a given lever displacement.

• Load check valve

Load check valve: Prevents reverse implement flow when the operator moves a valve from HOLD and system pressure is lower than the cylinder or work pressure. Without the load check valve, the implement would drift down. The load check valve will open to allow supply oil to flow through the control valve when the system pressure is higher than the work port pressure.

• Resolver

Resolver: Also called a double check valve. The resolver compares the signal between the valves and sends the highest resolved working pressure to the implement pump flow compensator. Although this slide shows the resolver and signal lines as external components, the resolver is actually inside the control valve, and the signal lines are internally drilled passages.

• Main control spool

Main control spool: Controls oil flow to the implement and contains three cross-drilled holes that connect to an axial drilled passage in the center of the control spool. The cross-drilled holes sense work port pressure in both the head and rod ends of the cylinders.

• Makeup valve

Makeup valve: Allows pressure in the tank to fill voids in the head end of the cylinders during times when cylinder supply pressure decreases below the tank pressure.

• Orifice

Orifice: Provides smoother implement operation by delaying the rate that the signal pressure in the flow control spring cavity decreases when the operator changes implement directions.

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NOTE: The throttling slot near the left end of the flow control spool spool is never completely closed, and the check valve does not completely block oil from reaching the main control spool. A small amount of oil meters through the flow control spool and past the load check valve to maintain a pressure at the main control spool that is equal to the flow control spool spring force. Maintaining pressure at the main control spool improves implement response. If the flow control spool is explained as a pressure reducing valve with a variable spring rate due to changes in signal pressure, the operation of the spool is easier to understand. The spool will limit the maximum pressure difference across the control spool to the value of the flow control spool spring and cylinder pressure to provide constant flow for a given lever displacement. INSTRUCTOR NOTE: For more information about the valve components and operation, refer to STMG 591 "446 Backhoe Loader--Steering and Implement Hydraulic System" (Form SESV1591).

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DOZER LIFT VALVE RAISE ROD END

HEAD END

RETURN TO TANK

FROM PREVIOUS VALVE

MAKEUP VALVE

PLUG

MAIN CONTROL SPOOL

RESOLVER

LOAD CHECK VALVE FROM PUMP

FLOW CONTROL SPOOL

TO COMPENSATOR VALVE

109 • Lift valve in RAISE • Spool shifts left

• Supply passage opened to rod end • Signal pressure sensed in flow control valve spring chamber

As the operator moves the lift control lever to the RAISE position, the control valve spool shifts to the left allowing pump supply to go through the quick-drop valve to the rod end of the cylinders and opens the head end of the cylinders to the tank. The oil will begin filling the rod end of the lift cylinders and begin raising the blade. Shifting the spool also opens the supply passage drilled in the center of the control valve spool to the rod end port. Pump pressure going to the lift cylinder or pressure from the rod end goes through the drilled passage in the control spool and this signal oil goes to two places. First, the oil travels through the orifice and fills the spring chamber of the flow control spool moving the spool to the left. As the control valve spool shifts to the left, the opening at the throttling slots near the left end of the spool increases so more oil can flow to the work port, while the throttling slots toward the right end of the control valve spool are open to the head end of the cylinder and to the tank. The amount of flow from the pump, combined with the amount of flow the lift work port needs, determines the distance that the flow control valve shifts.

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STMG 699 6/98 • Signal oil sent to resolver to upstroke pump

- 140 -

Also, the signal oil is sent to the resolver valve. If the lift circuit is producing the highest signal pressure, oil is sent through the manifold to the implement pump flow compensator valve. The pump will then upstroke to maintain the margin pressure, approximately 2100 kPa (305 psi) above the pressure of the signal oil.

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DOZER LIFT VALVE LOWER ROD END

HEAD END

RETURN TO TANK

FROM PREVIOUS VALVE

MAKEUP VALVE

PLUG

MAIN CONTROL SPOOL

RESOLVER

LOAD CHECK VALVE FROM PUMP

FLOW CONTROL SPOOL

TO COMPENSATOR VALVE

110 • Lift valve in LOWER • Spool shifts right • Supply oil goes to head end • Rod end opens to drain • Signal oil sent to resolver and flow control spring chamber • Head end passage contains makeup valve

This slide shows the operation of the lift control valve when the operator has selected the dozer LOWER position. The main control spool has shifted to the right opening a passage for supply oil to flow through the quick-drop valve to the head end of the cylinders and a passage for oil from the rod end of the cylinders to return to the tank. The main control spool movement allows the cylinder pressure to become signal oil that is directed to the resolver and the flow control spool spring chamber through the drilled passages in the main control spool. System pressure controls the upstroking of the pump by means of the resolver signal pressure and is the same as described in the dozer RAISE operation. The passage to the head end of the lift cylinders contains a makeup valve for the lift circuit. When the pressure in the cylinder supply passage decreases below the pressure in the tank, the makeup valve opens and allows return oil from the tank to fill voids in the head end of the cylinders. The makeup valve is needed because the weight of the blade tends to force oil out of the rod end of the cylinders faster than the pump can fill the head end of the cylinders. By including a makeup valve in the head end passage, the possibility of cavitation is greatly reduced.

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STMG 699 6/98 • Dozer LOWER has two conditions: - Normal lower - Quick-drop operation

- 142 -

The dozer lower operation can function in two conditions. If the control lever is moved up to 75% of its maximum non-float travel, the valve operates as previously described. However, if the operator continues to move the lever past this position, the quick-drop mode is activated. In FLOAT, detents are used to hold the control valve spool in the FLOAT position. No signal pressure is generated, which keeps the pump destroked. Both the rod and head ends of the lift cylinders are open to the tank, which allows the cylinder rods to move freely in either direction according to the amount and direction of the force on the blade. NOTE: Quick-drop valve operation will be discussed in greater detail later in this presentation.

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DOZER TILT VALVE TILT LEFT ROD END

HEAD END

PLUG

RETURN TO TANK

PLUG

MAIN CONTROL SPOOL

RESOLVER

LOAD CHECK VALVE FLOW CONTROL SPOOL

FROM PUMP

TO COMPENSATOR VALVE

111 • Blade tilt valve in TILT LEFT

• No makeup valves

The blade tilt valve is the third valve in the stack. The blade tilt control valve is a closed-center, manually operated valve controlled through mechanical linkage. The valve has three positions: TILT LEFT, HOLD, and TILT RIGHT. The valve has a centering spring to return the spool to the HOLD position when the operator releases the dozer control lever. This slide shows the position of the blade tilt control valve components during TILT LEFT operation. This valve functions basically the same as the blade lift control valve with several differences. When the valve spool shifts to the right, pump supply oil is directed to the head end of the cylinder, and the rod end of the cylinder is opened to drain. The load check valve and the resolver valve operate the same as the dozer lift valve. One major difference in the blade tilt valve is that no makeup valves are included in either the head end or rod end circuit. Since the pump can supply the necessary amount of oil to fill cylinder without cavitation, makeup valves are not necessary.

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RIPPER CONTROL VALVE HOLD ROD END

HEAD END

RETURN TO TANK

FROM PREVIOUS VALVE

MAKEUP VALVE

PLUG

MAIN CONTROL SPOOL

RESOLVER

LOAD CHECK VALVE FLOW CONTROL SPOOL

FROM PUMP

TO COMPENSATOR VALVE

112 • Ripper control valve in HOLD • Switch controls two functions • Diverter valve for ripper lift and tip

The ripper control valve is the first valve in the stack. The ripper control valve is a closed-center, manually operated valve controlled through mechanical linkage. The valve is used to raise and lower the ripper or to move the ripper shank IN and OUT. Both functions are controlled by the operator through the use of a switch located in the ripper control handle. The switch shifts a spool in the ripper diverter valve which directs oil to the correct circuit. The ripper control valve has a centering spring to return the valve spool to the HOLD position when the operator releases the lever. This slide shows the position of the ripper control valve components in HOLD. This valve functions basically the same as the blade lift control valve with several differences. When the main control spool shifts to the right, pump supply oil is directed to the head end of the ripper lift cylinders or to the head end of the ripper tip cylinders, and the rod end of the cylinders are opened to drain. The load check valve and the resolver valve operate the same as the dozer lift valve.

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STMG 699 6/98

• Head end passage contains makeup valve

- 145 -

The passage to the head ends of either the ripper lift or tip cylinders in the control valve contains a makeup valve. When the pressure in the cylinder supply passage decreases below the pressure in the tank, the makeup valve opens and allows return oil from the tank to fill voids in the head end of the cylinders. The makeup valve is needed because the weight of the ripper tends to force oil out of the rod end of the cylinders faster than the pump can fill the head end of the cylinders. By including a makeup valve in the head end, the possibility of cavitation is greatly reduced.

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D8R QUICK-DROP VALVE

D8R QUICK-DROP VALVE QUICK-DROP VALVE TO IMPLEMENT VALVE

TO ROD END

DOZER LIFT TO IMPLEMENT VALVE

TO HEAD END

TO IMPLEMENT VALVE DOZER TILT

113 Quick-drop Valve • Quick-drop valve (arrows) • Replaces two valves on earlier D8N

Shown in this slide is the schematic of the single quick-drop valve that replaces the two quick-drop valves that were mounted on the head end of both lift cylinders in the earlier machines. The valve (arrows) is mounted on top of the engine hood at the front of the machine. In the schematic, components in the quick-drop valve are shown with the dozer blade on the ground. The variable orifice sleeve is the essential component in the valve and functions to create the pressure necessary to move the valve spool to direct rod end oil to the head end in the QUICKDROP mode.

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QUICK-DROP VALVE HOLD

TO RIGHT CYLINDER HEAD END

TO LEFT CYLINDER HEAD END

TO RIGHT CYLINDER ROD END

TO LEFT CYLINDER ROD END

PASSAGE TO PLUNGER END VALVE SPOOL

PLUNGER

COVER

COVER

ORIFICE SLEEVE

PASSAGE TO SPOOL END TO/FROM LIFT CONTROL VALVE

114 • Quick-drop valve components: - Orifice sleeve - Plunger - Valve spool - Right and left covers - Spring

Shown in this view are the components of the single quick-drop valve: the orifice sleeve, the plunger, the valve spool, the right and left covers, and the spring. As shown in the previous slide, the valve components are shown with the dozer blade on the ground. Both the orifice sleeve and the plunger can float in the valve and their positions in HOLD depend on the previous action of the lift control valve: RAISE, LOWER, or FLOAT.

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QUICK-DROP VALVE DOZER RAISE

TO LEFT CYLINDER HEAD END

TO RIGHT CYLINDER HEAD END

TO RIGHT CYLINDER ROD END

TO LEFT CYLINDER ROD END

PASSAGE TO PLUNGER END PLUNGER

VALVE SPOOL

COVER

COVER

ORIFICE SLEEVE

PASSAGE TO SPOOL END TO/FROM LIFT CONTROL VALVE

115 • Quick-drop valve operation in RAISE • Rod end oil moves spool, plunger, and sleeve right

When the dozer control valve is moved to the RAISE position, supply oil enters the quick-drop valve through the passage on the left and moves the orifice sleeve to the right. The oil then flows out to the rod end of the cylinders. Return oil from the head end of the cylinders enters the valve and flows past the valve spool to the lift control valve. Return oil pressure then enters the passage to the plunger end inside the valve spool and is felt on the right end of the plunger. However, the blade RAISE pressure felt on the left end of the plunger is higher than the return oil pressure and keeps the plunger shifted to the right. Blade RAISE pressure also enters the passage to the right end of the spool. Since the same pressure is felt on the left end of the spool, the spring keeps the spool shifted to the right. NOTE: The orifice sleeve floats on the valve spool and is kept on the spool by a retaining ring.

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QUICK-DROP VALVE DOZER LOWER

TO LEFT CYLINDER HEAD END

TO RIGHT CYLINDER HEAD END

FROM LEFT CYLINDER ROD END

FROM RIGHT CYLINDER ROD END PASSAGE TO PLUNGER END

PLUNGER

VALVE SPOOL

COVER

COVER

ORIFICE SLEEVE PASSAGE TO SPOOL END TO/FROM LIFT CONTROL VALVE

116 • Quick-drop valve operation in LOWER • Rod end oil moves orifice sleeve left • Spring holds valve spool to the right

As the operator moves the lever to LOWER the blade (less than 75% of maximum travel), return oil from the rod end of the cylinders enters the quick-drop valve. The return oil flows past the orifice sleeve to the control valve and moves the orifice sleeve to the left against the retaining ring. This oil flow creates a pressure differential across the orifice sleeve. Supply oil (red) from the control valve enters the quick-drop valve and flows past the valve spool to the head end of the cylinders. Supply oil pressure enters the passage to the plunger end and is felt on the right end of the plunger. However, the return oil pressure (red dots) on the left end of the plunger is higher and keeps the plunger shifted to the right.

➥

STMG 699 6/98

- 150 -

Rod end return oil pressure (red and white stripes) enters the passage to the right end of the spool. This pressure is also felt on the major diameter at the left end of the spool just to the right of the orifice sleeve. In addition, return oil pressure, after the pressure drop across the orifice sleeve, is felt on the minor diameter at the left end of the spool. The net result is that the spool and plunger are kept to the right because of the spring and return pressure. The major diameters of the spool (the effective area at the right end and the effective area just to the right of the orifice sleeve) cancel each other. The pressure on the right end of the spool is not high enough to overcome the spring and return oil pressure on the minor diameter at the left end on the spool.

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QUICK-DROP VALVE QUICK-DROP

TO LEFT CYLINDER HEAD END

TO RIGHT CYLINDER HEAD END

FROM RIGHT CYLINDER ROD END

FROM LEFT CYLINDER ROD END

PASSAGE TO PLUNGER END VALVE SPOOL

PLUNGER

COVER

COVER

ORIFICE SLEEVE PASSAGE TO SPOOL END TO/FROM LIFT CONTROL VALVE

117 • Operation in QUICKDROP mode

When the dozer blade is rapidly lowered to the ground, the control valve lever has been moved more than 75% of the maximum travel, and the quick-drop valve operates in the QUICK-DROP mode.

• Flow across orifice sleeve creates differential

The increased lever travel results in higher cylinder rod end flow and a higher pressure drop across the orifice sleeve. The only difference from the dozer LOWER position is that the pressure drop across the orifice sleeve that is felt on the minor diameter of the right end of the spool overcomes the resistance of the spring, and the spool starts to move. The minimum flow that causes the necessary pressure drop across the orifice sleeve to begin spool movement is referred to as the "trigger point" and occurs at 75% of maximum lever travel. When the spool starts to move, the effective area of the orifice sleeve decreases and the pressure drop increases to shift the spool even farther.

➥

STMG 699 6/98

• Valve spool movement allows rod and head end oil to mix

- 152 -

The result is that the spool shifts completely to the left. This movement connects the rod end of the cylinders to the head end of the cylinders across the slots in the spool. This connection provides even less resistance and the downward blade velocity and flow from the rod ends increase. This connection also provides a "filling" function to minimize the pause time. Some of the oil from the rod ends still flows across the orifice sleeve causing a pressure drop to keep the spool shifted.

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QUICK-DROP VALVE DOZER LOWER WITH DOWN PRESSURE TO RIGHT CYLINDER HEAD END

TO LEFT CYLINDER HEAD END

FROM RIGHT CYLINDER ROD END

FROM LEFT CYLINDER ROD END

PASSAGE TO PLUNGER END PLUNGER

VALVE SPOOL

COVER

COVER

ORIFICE SLEEVE PASSAGE TO SPOOL END TO/FROM LIFT CONTROL VALVE

118 • LOWER WITH DOWN PRESSURE • When blade contacts ground, pause time occurs • Spool moves right and plunger moves left

When the blade contacts the ground and stops, flow from the rod end of the cylinders stops. With no pressure drop across the orifice, the spring shifts the spool to the right. After the pump fills the head end of the cylinders (pause time) and the head end cylinder pressure starts to increase, the blade begins to move down. Supply oil pressure (red) enters the passage to the right end of the plunger. Return oil pressure (red and white stripes) from the rod end of the cylinders is felt on the left end of the plunger. This pressure is lower than the oil pressure (red) on the right end of the plunger, and the plunger moves to the left. The pressure drop (red and white stripes) across the orifice sleeve that is felt on the minor diameter of the right end of the spool works to move the spool to the left. However, this movement is resisted by the spring and the supply oil pressure (red) acting on the plunger. Therefore, the spool stays shifted to the right.

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D8R RIPPER DIVERTER VALVE STEERING CHARGE PRESSURE

STEERING CHARGE PRESSURE PORT FROM RIPPER CONTROL VALVE

RIPPER TIP RIPPER LIFT

119 Diverter Valve • Diverter valve eliminates need for two control valves • Solenoid sends charge oil to move valve spool

• Pressure port used to diagnose problems

This slide shows the ripper diverter valve (arrow) with the control lever in the HOLD position. The operator can select any of the four ripper functions (RAISE, LOWER, TIP IN and TIP OUT) by using the control lever, which is equipped with a trigger switch. The trigger switch controls a solenoid on the ripper diverter valve that sends steering charge pressure oil to one end of the valve spool to shift the spool against the springs on the other end. Steering charge pressure at 2500 kPa (365 psi) is the same oil pressure used in the charge circuit for the steering pump and steering pilot valve. The charge pressure test port at the rear of the ripper diverter valve is used to diagnose ripper actuation problems. When the trigger switch is used, the solenoid is energized and charge pressure oil moves the diverter valve spool. Ripper TIP IN or TIP OUT can then be selected.

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RIPPER DIVERTER VALVE RIPPER TIP IN ( PORT E)

RIPPER TIP OUT (PORT F)

RIPPER LOWER (PORT C)

RIPPER RAISE (PORT D)

C CHARGE PRESSURE TEST PORT

E

RIPPER SUPPLY LOWER/TIP IN

D

F RIPPER SUPPLY RAISE/TIP OUT

120 • Letters below spool correlate to ripper cylinder ports

The letters below the ripper diverter valve spool relate directly to the ripper TIP IN, TIP OUT, RAISE and LOWER ports. The spool is shown in the solenoid DE-ENERGIZED position. If the operator moves the control lever, the ripper will RAISE or LOWER.

• Oil flow through diverter valve

For example, when the operator moves the lever to the RAISE position, oil from the control valve enters the ripper diverter valve through the RAISE/TIP OUT passage. Oil then flows into Passage D, goes through the valve body and flows out Port D to the rod end of the ripper raise cylinders. Return oil flows into Port C from the head end of the ripper cylinders, goes through the valve, flows out Passage C and returns to the ripper control valve through the LOWER/TIP IN passage.

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D8R STARTING AND CHARGING SYSTEM 200 BK

KEY START SWITCH

321 BR

BACK-UP ALARM

R

308 YL

109 RD C OFF S ON B ST 105 RD

KEY START 10 A

BACK-UP ALARM SWITCH

121 RD

10 A

BACK-UP ALARM 101 RD

304 WH

307 OR

STARTER RELAY 200 BK

BAT MTR STARTER MOTOR

MOTOR

306 GN

NEUTRAL-START SWITCH

200 BK

101 RD

109 RD 109 RD

MAIN RELAY

G

S RD 00

105 RD

112 PU

ALTERNATOR BREAKER

BUS BAR

109 RD

FRAME

RD 00

RD 00

DISCONNECT SWITCH

ENGINE BK 00

308 YL 200 BK

10 A FORWARD HORN

109 RD

10 A

POS NEG

ALT +

R

15 A

POS NEG

FRONT DASH DOME RD 00

SIDE AND REAR FLOOD LAMPS/RADIO RD 00

10 A

OPERATOR MONITOR

10 A

GAUGES AND SERVICE METER

15 A

WIPER MOTORS

15 A

CIGAR LIGHTER

POS NEG

POS NEG

BATTERIES

121 STARTING AND CHARGING SYSTEMS • Basic starting system: - Four batteries - Disconnect switch - Key start switch - Starter relay - Main relay • Basic charging system - Alternator - Alternator breaker - Bus bar

This schematic shows the components of the D8R starting and charging system. The basic starting system consists of the four batteries, the disconnect switch, the key start switch, the starter relay, and the main relay. With the disconnect switch closed, the negative potential of the batteries is connected to ground (frame). When the operator moves the key start switch to START, power is sent through the key start switch from the 105 RED wire to the 307 ORANGE and 308 YELLOW wires to energize the starter relay and main relay respectively. With the starter relay energized, power is sent to the starter motor through the 304 WHITE wire. After the engine has started, the key start switch is moved to ON and the main relay remains energized, which then provides power to five fuses through the 112 PURPLE wire. After the engine is started and running, the alternator will charge the batteries by directing power through the 109 RED wire, the alternator breaker, and the bus bar to the batteries. The bus bar is used as a junction block for the starter motor, the alternator, and the batteries.

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1

2

4 3

5

122 • Starting and charging system components: 1. Batteries 2. Starter 3. Alternator 4. Disconnect switch 5. Power outlet

The D8R starting and charging system uses four 3000 CCA 12-Volt maintenance free batteries (1) to provide the electrical power to the starter (2). A 50 amp alternator (3) is used to maintain the charge level of the batteries. An optional 75 amp alternator is available for additional accessories and when more than eight lights are required. The disconnect switch (4) is used to open and close the ground connection between the negative terminal of the batteries and the machine frame. The switch is convieniently located to the left of the operator's station. Next to the disconnect switch is the 24-Volt power outlet receptacle (5) that can be used to power service tools. Use the 4C9031 Battery to Tool Cable that has the standard cigarette lighter plug with an integral 1 amp fuse on one end and a standard MS 2-pin connector on the other.

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2

1

5 4

3

123 • Electrical components: 1. Auliliary start receptacle 2. Bus bar 3. Fuse panel

If the machine needs to be jump started, an auxiliary start receptacle (1) is standard equipment and is located on the left side of the engine. Two Plug Assemblies are available: the 8S2632 Plug Assembly is 2.45 m (10 ft.) long and the 9S3664 Plug Assembly is 3.81 m (15 ft.) long. If the plug assemblies are not available, refer to the procedure in the Operation Section of the Operation and Maintenance Manual for the D8R Track-type Tractor. A bus bar (2), located just below the operator's station on the left inside of the frame, is used as a junction to connect the positive power cable from the batteries to the starter. The auxiliary start receptacle and the prelubrication timer/solenoid are connected to the bus bar. Located on the left side of the operator's station just above the battery compartment is the fuse panel (3). The fuse panel contains fuses for the following circuits:

➥

STMG 699 6/98 - Flood lamps and radio - Operator monitor - Gauges and service meter - Wiper motor - Cigar lighter - Horn - Back-up alarm - Front dash dome - Key start switch - Blower motor - Alternator 4. Diagnostic connector 5. Main relay

- 159 -

-

Side and rear flood lamps and radio (15 amp) Operator monitor (10 amp) Gauges and service meter (10 amp) Wiper motor (15 amp) Cigar lighter (15 amp) Horn (10 amp) Back-up alarm (10 amp) Front dash dome (10 amp) Key start switch (10 amp) Blower motor (20 amp circuit breaker) Alternator (60 amp circuit breaker)

In the center of the panel is the diagnostic connector (4). The diagnostic connector can be used with the 6V2150 Starting/Charging Analyzer Group to analyze starting and charging problems. Use the Service Manual module "Systems Operation, Testing and Adjusting—Starting and Charging Systems for Machines Equipped with Diagnostic Connector" (Form SENR2947) when diagnosing problems in these systems. The main relay (5) is located just below the fuse panel. When the key start switch is moved to the ON position, the main relay is energized. Behind the fuse panel is the starter relay. When the key start switch is moved to START, the starter relay is activated and permits the starter to engage.

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1

2 3

4

5

124 • Electrical components: 1. Key start switch 2. Start aid switch 3. Neutral-start switch location 4. Ether starting aid 5. Coolant temperature switch

The key start switch (1) is located on the dash. If the dual twist tiller is in either FORWARD or REVERSE, the engine will not start because a neutral-start switch is installed in the dual twist tiller housing (3). The back-up alarm switch is also contained within the tiller housing. The ether starting aid group (4) is standard equipment. The group is located on the left side of the engine in front of the fuel injection pump. The operator can activate the system by depressing the start aid switch (2) on the dash. A coolant temperature switch (5) is located on the top right rear of the engine head. This system is not functional above 38°C (100°F). For the correct operating procedure, refer to the Operation Section of the D8R Track-type Tractor Operation and Maintenance Manual.

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3

2

1

125

ELECTRONIC MONITORING SYSTEM • EMS components: 1. EMS panel 2. Master fault light 3. Panel test switch

The Electronic Monitoring System (EMS) is designed to alert the operator of an immediate or impending problem in one or more of the machine systems. The system includes the following components: EMS Panel (1): contains eight fault lights, one for each machine system. Master Fault Light (2): flashes to indicate a Category 2 or 3 fault. Panel Test Switch (3): used to test the panel lights, the master fault light, and the fault alarm (not shown because it is located in the compartment with the pilot valve for the dual twist tiller). With the battery disconnect switch ON and the key start switch ON, holding the test switch in the UP position will allow all the panel lights and master fault light to flash. With the engine running, moving the test switch to the UP position will allow all the lights to flash and the fault alarm to sound. If any of the lights or alarm do not function, perform the necessary repairs before starting the engine again.

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D8R EMS PANEL COOLANT TEMPERATURE

POWER TRAIN OIL TEMPERATURE

COOLANT FLOW

POWER TRAIN OIL FILTER

ENGINE OIL PRESSURE

ALTERNATOR

HYDRAULIC OIL TEMPERATURE

HYDRAULIC OIL FILTER

126 • EMS warning categories • Category 1 - Alternator

The EMS panel has three warning categories: Category 1: For the first level of warning, only an LED indicator flashes. This alert informs the operator that a system requires attention, but a failure in the system will not endanger the operator or seriously damage any machine components.

• Category 2

- Alternator - Coolant temperature - Power train oil temperature - Hydraulic oil temperature

Category 2: For the second level of warning, both an LED indicator flashes and the master fault light flashes on and off. Second level warnings are caused by overheating and requires operator response. They inform the operator to change his method of operation to prevent high temperature damage to one or more systems. - Coolant Temperature - Power Train Oil Temperature - Hydraulic Oil Temperature

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STMG 699 6/98 • Category 3 - Engine oil pressure - Power train oil filter

- 163 -

Category 3: For the third level of warning, an LED indicator will flash, the master fault light will flash, and the fault alarm will sound. This alert requires the operator to immediately shut down the machine as safely and quickly as possible until the problem is corrected.

- Coolant flow

- Engine Oil Pressure

- Hydraulic oil filter

- Power Train Oil Filter - Coolant Flow - Hydraulic Oil Filter

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2 1

3

4

5

127 • Category 1 components: 1. Alternator 2. "R" terminal • Category 2 components: 3. Coolant temperature switch 4. Power train oil temperature switch 5. Hydraulic oil temperature switch

Category 1 Components: The alternator (1) is located on the right front of the engine. The "R" terminal (2) on the alternator provides an AC signal to the EMS control. The EMS control measures the frequency (Hz) of the AC signal and determines the speed at which the alternator is rotating. If the frequency measured is below 94 Hz ± 10%, the alternator alert indicator will FLASH. Category 2 Components: The 7N9785 Coolant Temperature Switch (3) is located at the left rear of the engine head. The switch opens at 107.2°C (225°F). The 3T8525 Power Train Oil Tmperature Switch (4) is located on the torque converter outlet relief valve. The switch opens at 129.4°C (265°F) and closes at 118.3°C (245°F). The 8N2248 Hydraulic Oil Temperature Switch (5) is located on the left side of the hydraulic tank. The switch opens at 101.7°C (215°F) and closes at 93.3°C (200°F).

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1 2

3

6

5 8

7

4

128 • Category 3 components: 1. Engine oil pressure switch 2. Power train oil filter 3. Hydraulic oil filter 4. Power train oil filter switch 5. Power train oil filter temperature switch

Category 3 Components: The 6T4949 Engine Oil Pressure Switch (1) is located at the right rear of the engine block. The switch opens at 93 kPa (13.5 psi) and closes at 69 kPa (10 psi). The 9X7781 Power Train Oil Filter Switch (4) is located at the front of the power train oil filter (2). The switch is normally open before installation. If the filter element becomes full of debris, the restriction will cause the pressure to increase inside the filter. If the pressure differential increases to 175 kPa (25 psi), the bypass valve will move and the power train oil filter switch will open causing the Category 3 Warning. Located on the rear of the filter is the 9G3341 Power Train Oil Filter Temperature Switch (5). The switch is normally closed below 52°C (125°F), which disables the Category 3 Warning. After the system is warm and if the filter is plugged, the fault will alert the operator.

➥

STMG 699 6/98 6. Hydraulic oil filter switch 7. Hydraulic oil filter temperature switch 8. Coolant flow switch

- 166 -

The 9X7781 Hydraulic Oil Filter Switch (6) is located at the rear of the hydraulic oil filter (3). The switch is normally open before installation. If the filter element becomes full of debris, the restriction will cause the pressure to increase inside the filter. If the pressure differential increases to 175 kPa (25 psi), the bypass valve will move and the power train oil filter switch will open causing the Category 3 Warning. Located on the front of the filter is the 8C3569 Hydraulic Oil Filter Temperature Switch (7). The switch is normally closed below 52°C (125°F), which disables the Category 3 Warning. After the system is warm and if the filter is plugged, the fault will alert the operator. The 3E2030 Coolant Flow Switch (8) is located at the right front side of the engine. The switch is normally open and, when the engine is running, coolant flow from the water pump moves the switch paddle closing the switch. If a loss of coolant flow causes the switch to open, the fault will alert the operator.

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129

• Fuel pressure switch (arrow)

The EMS Category 3 alarm is activated by the 9W3187 Fuel Pressure Switch (arrow) located on the filter housing. During normal operation (engine running), the fuel pressure switch is open. When the engine is stopped, the fuel pressure switch closes the alarm inhibit input to ground. With this input grounded, the alarm will NOT SOUND.

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1

2

3

4

130

• Four dash gauges: 1. Hydraulic oil temperature 2. Fuel level 3. Power train oil temperature 4. Engine coolant temperature

On the dash are four gauges for the operator to monitor the following systems: Hydraulic Oil Temperature (1): Monitors the temperature of the hydraulic oil system (implement and steering). Normal operating temperature is between 75°C and 96°C (167°F and 205°F). If the gauge indicator reaches 102°C (215°F), the temperature in the hydraulic system is too high. Move the cylinders without a load to reduce the temperature. Fuel Level (2): Monitors the amount of fuel in the tank. Power Train Oil Temperature (3): Monitors the temperature of the power train oil system. Normal operating temperature is between 82°C and 113°C (180°F and 235°F). If the gauge indicator reaches 129°C (265°F), the temperature in the power train oil system is too high. Move the tiller to NEUTRAL and maintain the engine rpm at HIGH IDLE to reduce the temperature. Engine Coolant Temperature (4): Monitors the temperature of the engine. Normal operating temperature is between 75°C and 93°C (167°F and 200°F). If the gauge indicator reaches 107°C (225°F) with the cooling system pressurized, the temperature is too high.

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2

1

4 3

131 • Gauge group component locations: 1. Hydraulic oil temperature sender 2. Fuel level sender

The 8N2248 Hydraulic Oil Temperature Sender (1) is located on the left side of the hydraulic tank. The 118-0690 Fuel Level Sender (2) is located in the top center of the fuel tank and, if an electrical problem occurs, a mechanical needle on the top of the sender shows the fuel level.

3. Power train oil temperature sender

The 8N3844 Power Train Oil Temperature Sender (3) is located on the torque converter outlet relief valve.

4. Engine coolant temperature sender

The 6N5926 Engine Coolant Temperature Sender (4) is located on the top front of the engine cylinder head.

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CONDENSER COIL COMPRESSOR

CONDENSER FAN

ORIFICE TUBE/ DRYER

EVAPORATOR COIL

ACCUMULATOR

D8R ORIFICE TUBE SYSTEM EVAPORATOR BLOWER FAN

132 AIR CONDITIONING SYSTEM • Air conditioning components: - Evaporator - Compressor - Condenser

The optional air conditioning system on the D8R contains the following components: Evaporator: Low pressure liquid refrigerant boils and collects heat from the surrounding area. Compressor: Increases the pressure and temperature of the refrigerant vapor.

- Orifice tube-dryer - Accumulator

Condenser: Removes heat from the high pressure/high temperature refrigerant vapor causing the vapor to change into high pressure liquid refrigerant. Orifice tube/dryer: Regulates the flow of refrigerant to the evaporator coil and the dryer section contains the desiccant for moisture removal. Accumulator: Functions as a liquid/vapor separator and ensures that only vapor will reach the compressor.

➥

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The optional air conditioning system in the D8R uses the Orifice Tube System. Instead of a thermostatic expansion valve used in earlier systems, an orifice tube is used. The orifice tube is installed in the dryer in the evaporator coil inlet line. The orifice tube has a fixed diameter and does not have the regulating capability of the expansion valve. Therefore, some refrigerant will leave the evaporator in the liquid form. The liquid refrigerant leaving the evaporator can damage the compressor. Therefore, an accumulator is located in the suction line after the evaporator. The accumulator acts as a liquid/vapor separator and ensures that only vapor will reach the compressor. In this system, the orifice tube is inserted into one end of the dryer. The orifice tube/dryer combination is commonly called the "in line dryer." The accumulator on the in line dryer system does not contain desiccant. The color codes for refrigerant used throughout this section are: Red

- High pressure liquid

Red and White Stripes

- Low pressure liquid

Purple

- High pressure gas

Purple and White Stripes

- Low pressure gas

Green

- Refrigerant oil

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1

2

133

• Air conditioning components: 1. Orifice tube/dryer 2. Moisture indicator

The orifice tube/dryer (1) is located on the left side of the engine just below the air cleaner housing. This group contains the orifice tube and the desiccant which dries the liquid refrigerant. Located on the left side of the orifice tube/dryer is the moisture indicator (2). The moisture indicator should be checked at the end of each shift. To check the moisture indicator, look at the color through the sight glass. If the color is blue, the system is dry. If the color is pink, the system has moisture. The moisture must be removed and the orifice tube/dryer must be changed.

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ORIFICE TUBE TUBE

SCREEN

TABS

O-RINGS

SCREEN

BODY

134 • Orifice tube components

The orifice tube contains a small tube which extends through the center of a plastic body. The two screens (one on each end) filter the refrigerant that flows through the small tube. The two o-rings are positioned to seal against leakage past the outside of the orifice tube. The two tabs engage the tooling when installing and removing the orifice tube.

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3

1 2

135

• Air conditioning components: 1. Compressor 2. Refrigerant switch

The compressor (1) is located at the left front of the engine. The refrigerant switch (2) is mounted on the compressor. The refrigerant switch is the low pressure sensing switch that is used to protect the system from damage due to the lack of oil. Located in the electrical circuit to the magnetic clutch, the switch opens and shuts off the compressor when the system pressure decreases below 175 kPa (25 psi).

3. Arc suppressor

The arc suppressor (3) is used to suppress the high voltage that is created each time the magnetic clutch on the compressor is engaged and released.

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DRIVE PLATE PULLEY ASSEMBLY

HUB

COMPRESSOR CLUTCH

SHAFT

BEARING COIL ASSEMBLY

136 • Magnetic clutch

The clutch is driven by the engine crankshaft through a belt to the pulley assembly on the magnetic clutch. The pulley assembly turns on the bearing and is not connected to the shaft. The drive plate is splined through the hub to the shaft. The coil assembly is mounted on the frame of the compressor and does not rotate. The electrical current from the thermostat creates a magnetic field in the coil assembly. The magnetic field pulls the drive plate against the pulley assembly. The pulley assembly then turns the drive plate, hub and shaft to operate the compressor.

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1 3

2

137

• Air conditioning components: 1. Accumulator 2. Condenser coil 3. Hydraulic cooler

The accumulator (1) is located just above and to the left of the compressor. The condenser coil (2) is located in front of the hydraulic system oil cooler (3) and behind the radiator.

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DIVERTER CAP

INLET

VAPOR LINE

ACCUMULATOR OIL BLEED LINE

OUTLET

138 • Accumulator components

The accumulator contains a diverter cap to keep the liquid away from the vapor line and an oil bleed line to allow oil to flow back to the compressor.

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8

2

3

7

4 5

6

10

9 1

139

• Heating and air conditioning controls: 1. Fan switch 2. Off 3. Low 4. High 5. Defrost 6. Low 7. High 8. Defogging 9. Heater temperature control 10. Air conditioning temperature control

The heating and air conditioning controls are located on the bottom left of the dash. The heating and air conditioning fan speed switch (1) has seven positions. Heating Positions: Off (2), Low (3), High (4), and Defrosting (5) Air Conditioning Positions: Low (6), High (7), and Defogging (8) The heater temperature control (9) can be rotated from OFF (left) to MAXIMUM (right) heat. The air conditioning temperature control (10) can be rotated from OFF (left) to MAXIMUM (right) cooling. NOTE: The heating system will be explained later in this presentation.

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2

1 3

4

5

140

2. Capillary tube

The evaporator coil (1) is located in front of the operator's station. The capillary tube (2) for the thermostatic switch is inserted into the evaporator coil. Moisture that drips off the evaporator coil is collected in a pan. This pan has a vinyl drip tube (3) that directs the water below the machine.

3. Evaporator drip tube

On top of the evaporator coil is the filter (4) that must be cleaned every 10 service hours or daily.

4. Filter

Inside the cab is a filter element (5) that must be cleaned every 10 service hours or daily.

• Air conditioning components: 1. Evaporator coil

5. Cab filter

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COMPRESSOR ELECTRICAL CIRCUIT

CAPILLARY TUBE

R-134a

CAPILLARY BELLOWS ASSEMBLY

PIVOTING FRAME

CLUTCH

POINT OPENING BATTERY

THERMOSTATIC SWITCH

TEMPERATURE ADJUSTING SCREW

141 • Thermostatic switch

The thermostatic switch in the compressor electrical circuit cycles the compressor, allowing the operator to adjust the amount of coolness desired and prevent the evaporator from freezing. The thermostatic switch consists of a pivoting frame attached to a capillary bellows assembly. The capillary tube is filled with refrigerant. The capillary tube is inserted between the evaporator core fins. The gas in the capillary tube expands or contracts, depending on the temperature of the evaporator. The expanding and contracting gas in the capillary tube causes the bellows to expand and contract. The expanding and contracting bellows cause the frame to pivot.

➥

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Half of the evaporator clutch coil contact is connected to the pivoting frame, and the other half is attached to the body of the switch. The contacts must come together to operate the compressor clutch. The operator regulates the evaporator cooling by varying the space between the contacts. Moving the contacts farther apart (decreasing cooling) causes the bellows to expand farther before closing the contacts. Moving the contacts closer together (increasing cooling) causes the contacts to close with less bellows movement. Adjustable thermostats have provisions for regulating the range between the opening and closing of the contacts. An adjustment screw is located below a removable cover. If an adjusment screw is not found in this location, the thermostat is non-adjustable.

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KEY START SWITCH

D8R OPERATOR'S STATION AIR CONDITIONING SYSTEM

R

308 YL

C OFF S ON B ST 105 RD 307 OR

KEY START 101 RD 10 A 304 WH

G

S

BAT MTR

STARTER RELAY

RD 00

200 BK

NEUTRAL-START SWITCH

109 RD

109 RD

MAIN RELAY

STARTER MOTOR

MOTOR

306 GN

112 PU

200 BK

101 RD

FRAME

BLOWER MOTOR

200 BK

BLOWER MOTOR

ENGINE RD 00

RD 00

308 YL

DISCONNECT SWITCH

BUS BAR

ALTERNATOR BREAKER

POS NEG

BK 00

POS NEG

109 RD ALT +

515 GY

515 GY

RD 00

RD 00

RESISTOR

R

POS NEG

POS NEG

BATTERIES

517 BU

516 GN 521 YL

BLOWER MOTOR BREAKER

ARC SUPPRESSOR

THERMOSTAT SWITCH

124 GN 20 A

1 2 5 4 3

513 OR

522 WH

T°

REFRIGERANT SWITCH (NORMALLY OPEN BEFORE REFRIGERANT CHARGE)

BLOWER MOTOR SWITCH

AIR CONDITIONER CLUTCH

142 • Air conditioning electrical schematic

The D8R air conditioning electrical system is very basic. Power for the air conditioner clutch comes from the refrigerant switch which is connected to terminal 2 on the blower motor switch. The thermostat switch is the control for the clutch. To increase or decrease the operator's station temperature, the operator rotates the thermostat switch on the dash to change the compressor cycling. The arc suppressor is used to suppress the high voltage that is created each time the magnetic clutch is engaged or released.

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1

2

143

• Air conditioner servicing: 1. Suction line 2. Discharge line

To check the air conditioning system, start and operate the engine at HIGH IDLE. Set the air conditioner control for maximum cooling and the fan control on HIGH. Allow two minutes for the system to stabilize. Feel the suction line (1) and the discharge line (2). If the system contains refrigerant, the discharge line will be warmer than the suction line. If the system does not contain or is very low on refrigerant, poor cooling output will result. Before faulting the refrigerant, check the condition and tightness of the compressor belt. The belt should deflect 14 to 20 mm (.56 to .81 in.) under a 110 N (25 lb.) force. If the belt tension is acceptable and the system still does not cool, the air conditioner system must be serviced.

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144

OPERATOR'S STATION HEATING SYSTEM • Heating system components: - Heater core

The optional heating system on the D8R contains the following components: Heater core: Source of heat to the operator from the engine coolant.

- Gate valves - Blower motors and fans - Fan speed control - Heater temperature control

Gate valves: Two valves, supply and return, that are used to control the flow of coolant to the heater core. Blower motors and fans: Provide forced air for both heating and cooling. Fan speed control: Seven position switch that controls the blower motors for heating and air conditioning. The switch uses a large resistor to provide the LOW speed. HIGH speed does not use the resistor. Heater temperature control: Controls the amount of coolant flow through the heater core.

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3

2

4

5

1

6

145

• Heating system components: 1. Heating fan switch 2. Off 3. Low 4. High 5. Defrosting 6. Heater temperature control

The heating controls are located on the bottom left corner of the dash. The heating fan speed switch (1) has seven positions. Heating Positions: Off (2), Low (3), High (4), and Defrosting (5) The heater temperature control (6) can be rotated from OFF (left) to MAXIMUM (right) heat.

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2

1

146

• Heater system components: 1. Blower motors 2. Resistor

The blower motors (1) have two speeds through the use of a power resistor (2). When the fan speed switch is moved to the LOW SPEED position, the resistor is connected in series and lowers the voltage to the motors, which decreases the speed of the motors.

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KEY START SWITCH

D8R OPERATOR'S STATION HEATING SYSTEM

R

308 YL

C OFF S ON B ST

KEY START 105 RD

10 A

101 RD

307 OR

304 WH

G

S

BAT MTR

STARTER RELAY

RD 00

200 BK

STARTER MOTOR

MOTOR

306 GN

NEUTRAL-START SWITCH

200 BK

101 RD

109 RD 109 RD

FRAME RD 00

308 YL

BLOWER MOTOR

200 BK

DISCONNECT SWITCH

BUS BAR

ALTERNATOR BREAKER

112 PU

MAIN RELAY

BLOWER MOTOR

ENGINE RD 00

POS NEG

BK 00

POS NEG

109 RD ALT +

RD 00

RESISTOR

R

RD 00 515 GY

515 GY

POS NEG

POS NEG

517 BU

516 GN

BATTERIES

124 GN 20 A

BLOWER MOTOR BREAKER

1 2 5 4 3

BLOWER MOTOR SWITCH

147 • Heating electrical schematic

The D8R heating electrical system is also very basic. Power for the two dual blower motors comes from the blower motor breaker, which is connected to the main relay. The blower motor switch can be wired for both heating and air conditioning. By using the resistor, two speeds are available: LOW and HIGH.

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148

• Heater control valve (arrow)

The heater control valve (arrow) is located in the return line of the heater core.

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149

• Heater control knob (arrow)

When the heater control knob (arrow) is rotated, the torsion cable, which connects the knob to the heater control valve, varies the amount of coolant that flows through the heater core.

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2

1

150

• Heater control components: 1. Supply valve 2. Return valve

The heater core shutoff valves are used when the ambient temperature is high enough that the operator does not need any cab heating. The upper valve (1) is the supply gate valve and the lower valve (2) is the return gate valve.

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151

CONCLUSION This presentation has discussed the major changes between the D8R and the D8N Track-type Tractors. All the systems of the machine were discussed and included the component locations and functions. For service repairs, adjustments, and maintenance, always refer to the Operation and Maintenance Manual, Service Manuals, and other related service publications.

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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. 42. 43. 44.

Title slide Steer system comparison Hydraulic system comparison Additional changes Optional equipment Operator's station Seat Steering controls Implement controls Brake pedal and engine speed controls Dash Disconnect switch Engine Air inlet and exhaust system Air filters Aftercooler Exhaust system Ether starting aid Fuel system Fuel tank Fuel tank valves Fuel level components Fuel system filters AMOCS radiator AMOCS coolant flow Radiator components Cooling system components Cooling system components Coolant monitoring system Engine oil system Engine oil system components Pre-lubrication system Pre-lubrication system (engine left side) Pre-lubrication system (engine right side) Pre-lubrication electrical schematic Undercarriage Pilot shaft dipstick Equalizer bar Power train comparison Power train schematic Torque divider Torque divider operation Power shift transmission Transmission pressure taps

45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63. 64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 7 5. 76. 77. 78. 79. 80. 81. 82. 83. 84.

Power shift transmission Power train fill tube Power train pumps Power train filter Transmission case drain plug Bevel gear case fast fill fitting Main sump drain Torque divider drain Torque converter outlet relief valve Power train oil cooler Power train schematic Transmission control valve--NEUTRAL Transmission control valve--FIRST FORWARD Transmission control valve--START IN GEAR Brake control, makeup and priority valve Brake control, makeup, and priority valve components Final drive, brakes, and steering differential and planetary Brake housing plugs Brake shuttle spool Pump drive lube tap Differential steer components Differential steer-- STRAIGHT LINE OPERATION Differential steer--LEFT TURN FORWARD Steering comparison Steering and implement systems diagram Pilot valve location Steering pump location Steering motor location Bypass and pressure control group location Bypass and pressure control group components Hydraulic tank and filter Hydraulic tank drain valve Hydraulic oil cooler Steering system schematic Pilot valve--NO TURN Steering pump--NO TURN Steering motor--NO TURN Steering motor flushing valve Pilot valve--LEFT TURN Steering pump--LEFT TURN

STMG 699 6/98

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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. 123. 124.

Steering pump (end view) Steering pump--LEFT TURN Steering pump (top view) Steering pump (side view) Bypass and pressure control group Steering and implement system diagram Hydraulic tank components Implement pump location Implement control valves location Lift cylinders Blade tilt cylinders Ripper components Ripper components Implement hydraulic system diagram Implement hydraulic system schematic Pressure and flow compensator valve Implement pump--ENGINE OFF Implement pump--LOW PRESSURE STANDBY Implement pump--UPSTROKING Implement pump--CONSTANT FLOW Implement pump--DESTROKING Implement pump--HIGH PRESSURE STALL Implement control valves schematic Dozer lift valve--HOLD Dozer lift valve--RAISE Dozer lift valve--LOWER Dozer tilt valve--HOLD Ripper valve--HOLD Quick-drop valve location Quick-drop valve--HOLD Quick-drop valve--RAISE Quick-drop valve--LOWER Quick-drop valve--QUICK-DROP Quick-drop valve--LOWER WITH DOWN PRESSSURE Ripper diverter valve schematic Ripper diverter valve Starting and charging system schematic Starting and charging system component Starting and charging system component locations Starting and charging system components locations

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.

EMS EMS panel EMS components--Categories 1 and 2 EMS components--Category 3 Fuel pressure switch Dash gauges Gauge components locations Air conditioning system Orifice tube dryer Orifice tube Air conditioning components Compressor clutch Air conditioning components Accumulator Heating and air conditioning controls Air conditioning components Thermostatic switch Air conditioning electrical schematic Air conditioning servicing Operator's station heating system Heating system controls Blower motors Heating system electrical schematic Heater control valve Heater control knob Heater shutoff valves D8R model view

CYLINDER

AIR CLEANER COMPRESSOR WHEEL

PRECLEANER

MUFFLER

DUST EJECTOR LINE

TURBINE WHEEL

TURBOCHARGER

- 194 -

HEAD AND VALVES

EXHAUST MANIFOLD

AFTERCOOLER

D8R AIR INLET AND EXHAUST SYSTEM

Directions: Draw the air flow lines between the components.

STMG 699 6/98 Serviceman's Handout No. 1

SUPPLY

TANK

DRAIN

TRANSFER PUMP PRIMARY FILTER

INJECTOR

- 195 -

SECONDARY FILTER

PRIMING PUMP

RETURN

D8R FUEL SYSTEM

Directions: Draw the fuel flow lines between the components.

STMG 699 6/98 Serviceman's Handout No. 2

BYPASS

WATER PUMP

TEMPERATURE REGULATOR

SHUNT LINE

WATER PUMP OUTLET

AIR VENT

AIR FLOW

- 196 -

OIL COOLER

AFTERCOOLER

EXPANSION TANK

D8R ADVANCED MODULAR COOLING SYSTEM

Directions: Draw the coolant flow arrows between the components.

STMG 699 6/98 Serviceman's Handout No. 3

D8R LUBRICATION SYSTEM

Directions: Fill in the blanks with the correct name for each component.

STMG 699 6/98 - 197 Serviceman's Handout No. 4

109 RD

+

ALT

R

KEY START 10 A

112 PU

109 RD

10 A

RD 00

BUS BAR

OPERATOR MONITOR GAUGES AND SERVICE METER WIPER MOTORS CIGAR LIGHTER

10 A 10 A 15 A 15 A

116 BR

SIDE AND REAR FLOOD LAMPS/RADIO

10 A FRONT DASH DOME

105 RD

101 RD

337 WH

ALTERNATOR BREAKER

101 RD

10 A FORWARD HORN

15 A

121 RD

BACK-UP ALARM

109 RD

109 RD

NEUTRAL-START SWITCH

307 OR

105 RD

306 GN

200 BK

109 RD

200 BK

C OFF S ON B ST

R

BACK-UP ALARM

200 BK

RD 00

RD 00

G

BK 00

STARTER MOTOR/ PRELUBE

POS NEG

BATTERIES

POS NEG

200 BK

A447 PK

337 WH

307 OR

PRELUBE TIMER/ SOLENOID

DISCONNECT SWITCH

101RD

301 BU

OIL PRESSURE CUTOFF SWITCH

POS NEG

RD 00

POS NEG

RD 00

ENGINE

MOTOR

BAT MTR

S

FRAME

200 BK

304 WH

116 BR

BACK-UP ALARM SWITCH

321 BR

- 198 -

308 YL

MAIN RELAY

STARTER RELAY

308 YL

KEY START SWITCH

D8R PRE-LUBRICATION SYSTEM

Directions: Draw the wires between the components of the pre-lubrication system.

STMG 699 6/98 Serviceman's Handout No. 5

STMG 699 6/98

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Serviceman's Handout No. 6

Directions: Match the components with the associated letter.

D8R COMPONENT IDENTIFICATION Q

R

O P

A

J

B C

G

D

H

E

I

F

M L

K

N

Case Drain Filter

Bevel Gear Case

Implement Pump

Tiller Lever and Pilot Valve

Quick-drop Valve

Steering Motor

Oil Cooler

Steering Pump

Brake Housing

Hydraulic Tank

Torque Divider

Power Train Filter

Bypass and Pressure Control Group Hydraulic Tank Charge Pump Final Drive

Power Train Pumps Implement Filter

TORQUE DIVIDER

Directions: Fill in the blanks with the correct name for each component.

STMG 699 6/98 - 200 Serviceman's Handout No. 7

POWER SHIFT TRANSMISSION

Directions: Fill in the blanks with the correct name for each component.

STMG 699 6/98 - 201 -

Serviceman's Handout No. 8

P3

R N F

1 2 3

P1

3

5 4

2

1

P2

D8R POWER TRAIN HYDRAULIC SYSTEM

Directions: Fill in the blanks with the correct name for each component.

STMG 699 6/98 - 202 -

Serviceman's Handout No. 9

P3

A

P1

B

3

4

2

1

C

P2

- 203 -

R N F

1 2 3

5

NEUTRAL

D8R TRANSMISSION CONTROL VALVE

Directions: Fill in the blanks with the correct name for each component.

STMG 699 6/98 Serviceman's Handout No. 10

BRAKE CONTROL, MAKEUP AND PRIORITY VALVE GROUP

Directions: Fill in the blanks with the correct name for each component.

STMG 699 6/98 - 204 -

Serviceman's Handout No. 11

STMG 699 6/98

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Serviceman's Handout No. 12

Directions: Write the sequence of letters for the power flow through the differential power train for the condition: LEFT TURN FORWARD. Use the numbered blanks at the bottom of the page for the two power flow splits.

HYDRAULIC MOTOR

P B J TO LEFT FINAL DRIVE

F

C

A

G E

I D

TRANSMISSION INPUT

H

K M

N

L

O I

N

J

G

E F

P

TO RIGHT FINAL DRIVE

M H K

C

DRIVE PLANETARY STEER PLANETARY

EQUALIZING PLANETARY

1. _________

1. _________

7. _________

2. _________

2. _________

8. _________

3. _________

3. _________

4. _________

4. _________ 5. _________ 6. _________

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Serviceman's Handout No. 13

Steering System Component Reference Checklist I Directions: Use this sheet to take notes during the presentation and as a checklist when identifying components during the lab session _____ Charge pressure relief valve Example: Limits charge pressure for the charging circuit, ripper diverter valve and pilot valve. _____ Pressure compensator (cutoff) valve

_____ Right and left crossover and makeup relief valves

_____ Charge pump

_____ Pump control spool

_____ Pump control piston

_____ Steering pump swashplate and pistons

_____ Steering motor with flushing valve

_____ Steering charge circuit filter

_____ Cold oil bypass valve

_____ Cooler

_____ Cooler bypass valve

_____ Pressure reducing valve and check valve

_____ Orifice in bypass and pressure control group

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Serviceman's Handout No. 14

Implement System Component Reference Checklist II Directions: Use this sheet to take notes during the presentation and as a checklist when identifying components during the lab session _____ Flow compensator (margin) spool Example: Maintains difference between supply pressure and signal pressure. _____ Pressure compensator (cutoff) spool

_____ Quick-drop valve

_____ Ripper diverter solenoid

_____ Ripper diverter spool

_____ Charging valve

_____ Main relief valve

_____ Hydraulic line from implement pump to bypass and pressure control group

_____ Bleed valve on pump compensator valve

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Serviceman's Handout No. 15

Directions: Match the components of the D8R Differential Steer System to the definitions at the right of the page. Place the letter in the blank next to the name. _____ Pilot Valve _____ Cooler Bypass Valve _____ Pump Control Piston

A. Fills the system with oil during start-up and provides cool oil for the drive loops and steering pilot valve. B. When either side of the loop reaches 40000 kPa (5800 psi), this valve destrokes the pump.

_____ Pressure Compensator (Cutoff) Valve _____ Pump Control Spool _____ Cold Oil Bypass Valve _____ Orifice in Bypass and Pressure Control Group _____ Steering Motor with Flushing Valve _____ Charge Pump _____ Pressure Reducing Valve and Check Valve

C. This valve limits the charge pressure to 2500 kPa (365 psi). D. Each side of the drive loop has a valve that limits the pressure spikes. E. Pilot oil moves the spool a small amount and directs charge pressure to either end of the pump control piston. F. Contains two pressure reducing valves which control the displacement of the steering pump. G. Uses flow from the steering pump to cause the machine to make right or left turns.

_____ Charge Pressure Relief Valve H. Filters charge pump oil. _____ Right and Left Crossover and Makeup Relief Valves _____ Steering Charge Circuit Filter _____ Bypass and Pressure Control Group

I. This valve group serves as a collection manifold for the charge pressure and cooling circuit of the steering system. J. This valve protects the charge circuit when the oil is cold. K. This valve protects the cooler from differential pressures higher than 345 kPa (50 psi). L. If charge pump pressure decreases below a set pressure, oil from the implement pump oil helps replenish the charge circuit. M. Steering pump case drain oil directed to steering motor. N. Directly connected to the swashplate.

D8R STEERING AND IMPLEMENT HYDRAULIC SYSTEM

Directions: Fill in the blanks with the correct name for each component.

STMG 699 6/98 - 209 Serviceman's Handout No. 17

ENGINE OFF

PUMP AND COMPENSATOR OPERATION

Directions: Fill in the blanks with the correct name for each component.

STMG 699 6/98 - 210 Serviceman's Handout No. 18

HOLD

DOZER LIFT VALVE

Directions: Fill in the blanks with the correct name for each component.

STMG 699 6/98 - 211 Serviceman's Handout No. 19

HOLD

QUICK-DROP OPERATION

Directions: Fill in the blanks with the correct name for each component.

STMG 699 6/98 - 212 Serviceman's Handout No. 20

109 RD

+

ALT

R

200 BK

109 RD

200 BK

109 RD

10 A

105 RD

101 RD

121 RD 304 WH

SIDE AND REAR FLOOD LAMPS/RADIO OPERATOR MONITOR GAUGES AND SERVICE METER WIPER MOTORS CIGAR LIGHTER

10 A 10 A 15 A 15 A

RD 00

200 BK

G

STARTER MOTOR

POS NEG

POS NEG

BATTERIES

POS NEG

RD 00

POS NEG

RD 00

ENGINE

MOTOR

BAT MTR

S

BACK-UP ALARM SWITCH

FRAME

200 BK

RD 00

BUS BAR

RD 00

15 A

10 A FRONT DASH DOME

ALTERNATOR BREAKER

109 RD

101 RD

BACK-UP ALARM 10 A

FORWARD HORN

109 RD

NEUTRAL-START SWITCH

10 A

KEY START

112 PU

306 GN

307 OR

105 RD

C OFF S ON B ST

R

BACK-UP ALARM

321 BR

BK 00

DISCONNECT SWITCH

- 213 -

308 YL

MAIN RELAY

STARTER RELAY

308 YL

KEY START SWITCH

D8R STARTING AND CHARGING SYSTEM

Directions: Draw the wires between the components of the starting and charging system.

STMG 699 6/98 Serviceman's Handout No. 21

D8R EMS PANEL

Directions: Fill in the blanks with the correct name for each symbol.

STMG 699 6/98 - 214 Serviceman's Handout No. 22

Directions: Fill in the blanks with the correct name for each component.

D8R ORIFICE TUBE SYSTEM

STMG 699 6/98 - 215 Serviceman's Handout No. 23

109 RD

+

ALT

112 PU

109 RD

BLOWER MOTOR SWITCH

20 A

1 2 5 4 3

516 GN 124 GN

515 GY 515 GY

ALTERNATOR BREAKER

101 RD

BLOWER MOTOR

NEUTRAL-START SWITCH

10 A

KEY START

517 BU

RD 00

G

POS NEG

513 OR

DISCONNECT SWITCH

T°

AIR CONDITIONER CLUTCH

522 WH

THERMOSTAT SWITCH

BATTERIES

BK 00

ARC SUPPRESSOR

POS NEG

REFRIGERANT SWITCH (NORMALLY OPEN BEFORE REFRIGERANT CHARGE)

POS NEG

RD 00

POS NEG

RD 00

MOTOR

STARTER

ENGINE

MOTOR

BAT MTR

S

FRAME

200 BK

RD 00

BUS BAR

521 YL

RESISTOR

BLOWER MOTOR

101 RD

RD 00

304 WH

D8R OPERATOR'S STATION AIR CONDITIONING SYSTEM

- 216 -

BLOWER MOTOR BREAKER

R

200 BK

109 RD

306 GN

307 OR

105 RD

C OFF S ON B ST

R

200 BK

308 YL

MAIN RELAY

STARTER RELAY

308 YL

KEY START SWITCH

Directions: Draw the wires between the components of the air conditioning electrical system.

STMG 699 6/98 Serviceman's Handout No. 24

+

ALT

R

200 BK

109 RD

200 BK

515 GY

1 2 5 4 3

516 GN 124 GN

515 GY

BLOWER MOTOR

ALTERNATOR BREAKER

101 RD

RD 00

G

POS NEG

POS NEG

BATTERIES

POS NEG

RD 00

POS NEG

RD 00

BK 00

STARTER MOTOR

ENGINE

MOTOR

BAT MTR

S

FRAME

200 BK

RD 00

BUS BAR

BLOWER MOTOR SWITCH

517 BU

RESISTOR

BLOWER MOTOR

101 RD

RD 00

304 WH

DISCONNECT SWITCH

D8R OPERATOR'S STATION HEATING SYSTEM

- 217 -

BLOWER MOTOR BREAKER

20 A

109 RD

NEUTRAL-START SWITCH

KEY START 10 A

112 PU

306 GN

307 OR

105 RD

C OFF S ON B ST

R

109 RD

308 YL

MAIN RELAY

STARTER RELAY

308 YL

KEY START SWITCH

Directions: Draw the wires between the components of the heating electrical system.

STMG 699 6/98 Serviceman's Handout No. 25

STMG 699 6/98

- 218 -

INSTRUCTOR NOTES

STMG 699 6/98

- 219 -

INSTRUCTOR NOTES

SESV1699 6/98

Printed in U.S.A.