Automatic Transmission: Front-wheel Drive Automatic Transaxle Repair

automatic transmission

front-wheel drive automatic transaxle repair student reference book

COURSE CODE: 37S05T0 ORDER NUMBER: FCS-13882-REF September 2, 2004

Ford Customer Service Division Technical Training

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Appropriate service methods and proper repair procedures are essential for the safe, reliable operation of all motor vehicles, as well as the personal safety of the individual doing the work. This document provides general directions for accomplishing service and repair work with tested, effective techniques. Following them will help assure reliability. There are numerous variations in procedures, techniques, tools, and parts for servicing vehicles, as well as in the skill of the individual doing the work. This document cannot possibly anticipate all such variations and provide advice or cautions as to each. Accordingly, anyone who departs from instructions provided in this document must first establish that he compromises neither his personal safety nor the vehicle integrity by his choice of methods, tools or parts. As you read through the shop manual procedures, you will come across NOTES, CAUTIONS, and WARNINGS. Each one is there for a specific purpose. NOTES give you added information that will help you to complete a particular procedure. CAUTIONS are given to prevent you from making an error that could damage the

vehicle. WARNINGS remind you to be especially careful in those areas where carelessness can cause personal injury. The following list contains some general WARNINGS that you should follow when you work on a vehicle. Always wear safety glasses for eye protection. Use safety stands whenever a procedure requires you to be under the vehicle. Be sure that the ignition switch is always in the OFF position, unless otherwise required by the procedure. Set the parking brake when working on the vehicle. If you have an automatic transmission, set it in PARK unless instructed otherwise for a specific service operation. Operate the engine only in a well-ventilated area to avoid the danger of carbon monoxide. Keep yourself and your clothing away from moving part when the engine is running, especially the fan and belts. To prevent serious burns, avoid contact with hot metal parts such as the radiator, exhaust manifold, tail pipe, catalytic converter and muffler. Do not smoke while working on the vehicle. To avoid injury, always remove rings, watches, loose hanging jewelry, and loose clothing before beginning to work on a vehicle. Tie long hair securely behind your head. Keep hands and other objects clear of the radiator fan blades. Electric cooling fans can start to operate at any time by an increase in under hood temperatures, even though the ignition is in the OFF position. Therefore, care should be taken to ensure that the electric cooling fan is completely disconnected when working under the hood.

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The Automatic Transmission Curriculum consists of 8 courses addressing automatic transmission theory of operation, diagnosis, and service. Each course in the curriculum is a “building block” for the next course in the curriculum. This curriculum is designed for technicians who want to learn the methods and techniques to properly diagnose and service automatic transmission systems and components. The skills and knowledge gained from this curriculum will enable technicians to pursue training in other service specialty areas. The Automatic Transmission Update course is a Web-based Training (WBT) course designed as an ongoing source of information on new transmissions/transaxles. The course is required for currently certified technicians. New technicians do not have to take it. Currently this course addresses the Torqshift transmission. Future versions of the course will cover new content.

All technicians will be required to take future versions of the Automatic Transmission Update course to remain certified. Technicians will be notified of need to take the course by electronic field communication. When technicians take the course, it sets the time clock for when they have to take the next update course.

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The Automatic Transmission Curriculum consists of 8 courses addressing automatic transmission theory of operation, diagnosis, and service. Each course in the curriculum is a “building block” for the next course in the curriculum. This curriculum is designed for technicians who want to learn the methods and techniques to properly diagnose and service automatic transmission systems and components. The skills and knowledge gained from this curriculum will enable technicians to pursue training in other service specialty areas.

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In a typical transaxle, power flow also enters at the torque converter. At this point the transaxle uses a chain or set of gears to transfer power to the input shaft. Some of the power passes into the pump’s input shaft and drives the fluid pump. The output shaft transfers power to the transaxle’s final drive assembly which directs the power flow to each drive wheel.

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The 4F50N/AX4N automatic transaxle is a four-speed unit with electronic shift control. It is designed for operation in a transverse power train for front-wheel drive vehicles. It has the following major components: x case with chain cover x chain drive x two friction bands: overdrive, coast x five friction clutches: forward, direct, intermediate, reverse, low-intermediate (AX4S – low intermediate clutch not present) x three one-way clutches: low, direct, low-intermediate (AX4S – low intermediate one-way clutch not present) x a front and rear simple planetary gear set x final drive planetary gear set x differential x pump assembly x main control Synchronized – two hydraulic events in a single shift, for example on the AX4S the low/intermediate band is applied and released to achieve different gears.

Non-synchronized – one hydraulic event in a single shift (apply or release), for example on the AX4N the low/intermediate clutch remains applied for all forward gears but has no effect on some gears.

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The torque converter is a standard four-element device: x x x x

impeller assembly turbine assembly stator/reactor assembly clutch and damper assembly

The standard torque converter components operate as follows: x x x x

Rotation of the converter housing and impeller set the fluid in motion. The turbine reacts to the fluid motion from the impeller, transferring rotation to the gear train through the input shaft. The stator (also called reactor) redirects fluid going back into the impeller, providing for torque multiplication. The clutch and damper assembly dampens power train torsional vibration and provides a direct mechanical connection for improved efficiency.

x

Power is transmitted from the torque converter to the planetary gear sets and other components through the input shaft.

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The hydraulic system has a main control assembly. The pump assembly, hydraulic control valves and electro-hydraulic actuators are located in the main control. Gaskets are used for the separator plate between the pump body and valve body. The separator plate between the valve body and chain cover has integral gaskets.

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The gear train consists of: x planetary gear sets x apply components x final drive gear set x differential Planetary Gear Set The transaxle has two planetary gear sets to provide operation in reverse and four forward speeds. The gear sets are comprised of the following components: x front sun gear (part of the front sun gear and shell assembly) x front carrier x rear ring gear x front ring gear and rear carrier x rear sun gear

The sun gear is splined to the front ring gear and rear carrier of the planetary gear sets. The sun gear acts as the driving member and the carrier as the driven member. The ring gear is held stationary inside the case using lugged teeth. Turbine Shaft The turbine shaft is splined to both the torque converter stator and the drive sprocket. This allows input torque to be transmitted from the torque converter to the drive chain and driven sprocket. Output Shaft The output shaft is splined to one of the differential side gears on one end, supported by the driven sprocket and driven sprocket support on the other end. This allows power flow through the differential for even output torque to the drive axles. Drive Chain and Sprockets A chain drive transfers torque from the torque converter turbine to the planetary gear sets. The chain drive is composed of the following components: x drive sprocket x driven sprocket x drive chain The transaxle case has a support for the drive sprocket that also serves as the support for the torque converter stator. A driven sprocket support mounts in the barrel of the transaxle case and also supports the clutches and gear set components. Final Drive Gear Set The final drive consists of a planetary gear set that transfers and multiplies torque from the planetary gear sets to the differential. The final drive consists of the following components: x sun gear x carrier (part of the differential case) x ring gear Differential The differential allows the half shafts and wheels to rotate at different speeds during cornering. The differential assembly consists of the following components: x differential case (part of the final drive carrier) x two pinion gears supported by a pinion shaft x two side gears supported by the differential case and half shafts

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The 4F27E was introduced with the 2000 Focus. It is a fully automatic, electronically controlled four-speed transmission designed for front-wheel-drive vehicles. The designation 4F27E means: x

4 — 4-four-speed transmission

x

F — front wheel drive

x

27 — originally designed for maximum input torque after torque converter: 365 Nm (270 lb-ft)

x

E — fully electronic control

The individual ratios are achieved through two planetary gear sets, connected one behind the other. The individual components of the planetary gear sets are driven or held by means of four multi-plate clutches, a band and a roller one-way clutch.

Torque is transmitted to the final drive assembly through an intermediate gear stage. The electrical and hydraulic functions are carried out by an EEC V Powertrain Control Module (PCM). The manual selector lever gives the driver a choice of "P", "R", "N", "1", "2" and "D". In drive range "D" it is also possible to operate an O/D switch on the manual selector lever to prevent the transmission from shifting into fourth gear or, if already in fourth, shifting down to third gear. To minimize fuel consumption, the torque converter clutch is applied by the PCM in 3rd and 4th gears depending on the throttle position and vehicle speed. The transmission has Electronic Synchronous Shift Control (ESSC), which guarantees extremely smooth gear shifting over the entire life of the transmission. A hydraulic emergency operating program maintains limited operation in the event of failure of important electrical components. Default is 3rd gear. The transmission can be tested using a scan tool through the Data Link Connector (DLC) in the passenger compartment.

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The torque converter is a standard four-element device: x x x x

impeller assembly turbine assembly stator/reactor assembly clutch and damper assembly

The standard torque converter components operate as follows: x x x x x

Rotation of the converter housing and impeller set the fluid in motion. The turbine reacts to the fluid motion from the impeller, transferring rotation to the gear train through the input shaft. The stator/reactor redirects fluid going back into the impeller, providing for torque multiplication. The clutch and damper assembly dampens power train torsional vibration and provides a direct mechanical connection for improved efficiency. Power is transmitted from the torque converter to the planetary gear sets and other components through the input shaft.

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Individual ratios are selected by means of four multi-plate clutches, a brake band, and a roller one-way clutch. These components are controlled by the PCM through pulse width modulated (PWM) solenoid valves in the valve body. The valve body contains six solenoids: x x x

three PWM solenoids two shift solenoids (on/off) one main regulating solenoid (variable force solenoid- EPC).

The individual clutches and bands are supplied pressure from the PWM solenoid valves and the shift solenoid (on/off) valves. These valves allow direct actuation of clutches and bands to ensure extremely smooth gear shifting through precise pressure regulation.

The shift solenoid (on/off) valves switch the hydraulic path to the clutches and bands, reducing the number of required modulating valves. The main regulating valve (variable force solenoid) ensures that sufficient hydraulic pressure is available in all operating conditions. PWM solenoid 1-3 PWM solenoids 1, 2 and 3 control the pressure to the bands and clutches. Shift solenoid (on/off) 1 and 2 The shift solenoids (on/off) switch the different oil passages in the valve body to direct the pressure to the individual clutches and bands. Main regulating solenoid The main regulating solenoid controls the required main line pressure (based on engine load) for the individual transmission ranges. Electronic Synchronous Shift Control (ESSC) ESSC monitors shift operations to adapt to the wear in the shift elements over the life of the transmission. This is possible since the shift elements are actuated by modulated valves. If the PCM detects a deviation from the stored values for the shift time and synchronization of the shift operation, the pressure buildup or reduction is adapted accordingly.

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The final drive input gear is splined to the planet carrier of the front planetary gear set and drives the transfer shaft input gear of the intermediate gear stage. The transfer shaft output gear of the intermediate gear stage drives the final drive assembly. Torque is transmitted to the half shafts through the final drive assembly. The differential allows the half shafts and wheels to rotate at different speeds during cornering. The intermediate gear stage is designed such that final drive ratio can be adapted for different vehicle applications.

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To properly diagnose a concern have the following publications available in DVD format: x Powertrain Control/Emissions Diagnosis (PC/ED) manual x TSBs and OASIS Messages x Wiring Diagrams x Workshop Manuals These publications provide the information required for diagnosing transmission concerns. Additionally, the Blue Books provide detailed color information and diagrams that can be extremely useful.

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When internal wear or damage has occurred in the transaxle, metal particles, clutch plate material, or band material may have been carried into the torque converter and transaxle fluid cooler. These contaminants are a major cause of recurring transaxle troubles and must be removed from the system before the transaxle is put back into use.

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