Automatic Transmission - Mechanism & Function: Other Subaru Outback BP

CONSTRUCTION

The pump consists of a parachoid rotor pair, a housing and a cover. The inner rotor has nine teeth and the outer rotor has ten teeth.

Scheme 715

Scheme 716

1. The pump draws automatic transmission fluid (ATF) from the oil pan through the oil strainer located under the hydraulic control valve assembly. The ATF then flows through a passage in the transmission case, and after passing through the oil pump housing and oil pump cover, it enters the suction port.
2. As the inner rotor rotates, the outer rotor also rotates. This motion causes the ATF to be sucked up through the suction port and discharged from the discharge port.
3. The discharged ATF flows through a passage in the oil pump cover and then a passage in the oil pump housing. It then goes through a passage in the transmission case to the pressure regulator valve in the control valve assembly, from which the ATF is directed to various clutches, brakes, and torque converter lock-up clutch for acting as hydraulic fluid and lubricating oil. Part of the ATF also flows, directly and after passing through the regulator valve, to the manual valve, from where it is distributed to the circuit corresponding to the range selected by the selector lever.
4. As engine speed increases, the delivery rate of the oil pump also increases.

Scheme 717

WHEN REVERSE IS SELECTED

Hydraulic pressure from the hydraulic control valve is applied to the reverse clutch piston when a shift is made into the reverse. The drive and driven plates are pressed together by this pressure, so that the engine torque from the high clutch drum is transmitted to the front sun gear through the 2-4 brake hub.

Scheme 718

WHEN REVERSE IS NOT SELECTED

When the selector lever is in any position other than the reverse, no pressure is applied to the reverse clutch piston. Hence the drive and driven plates are separated from each other, transmitting no power to any element beyond them.

A check ball is built into the clutch piston. This check ball has a function of releasing the pressure which may build up in the fluid remaining behind the piston by centrifugal force generated by the idly rotating high clutch drum, thereby avoiding a half-engaged state of the clutch.

Scheme 719

High Clutch

When the 3rd or 4th gear is selected, hydraulic pressures are applied to the high clutch from the shift valve and pressure regulator valve. The clutch drive and driven plates are pressed together, thus transmitting the engine power from the input shaft to the front planetary carrier through the high clutch hub.

A cover is placed inside the piston, and the space between the piston and the cover is filled with ATF. When the high clutch is not in engagement, the centrifugal force generated in the ATF inside the cover cancels out the centrifugal force generated in the ATF remaining behind the high clutch piston, thus preventing incomplete disengagement of the clutch.

When the high clutch is engaged, the pressure pushing the clutch piston is much larger than the counteracting force of the ATF in the cover, so the clutch remains engaged.

Scheme 720

The 2-4 brake consists of a 2-4 brake piston, a return spring, a pressure plate, drive plates and driven plates.

This brake is engaged by the hydraulic pressure from the transmission control valve and locks the front sun gear when the 2nd gear is selected in the D, 3 or 2 range, or when the 4th gear is selected in the D range.

Scheme 721

The low & reverse brake consists of a piston, a dish plate, drive plates, driven plates, a retainer plate and a snap ring that are placed in a housing formed in the transmission case.

Scheme 722

When the 1st gear is selected in the 1 range or the reverse is selected, the pressure from the pressure regulator valve is applied to the low & reverse brake piston. The piston then presses the drive and driven plates together and causes the low & reverse brake to lock.

The low clutch consists of a drum, piston, return springs, cover, drive plates, driven plates, one-way clutch, and other sealing and retaining elements.

The low clutch drum is made of a press-formed metal sheet. The drum's outer race and sleeve are welded together to the drum by an electron beam welding technique.

Scheme 723

The low clutch operates in the D range (1st, 2nd, and 3rd gears), 3 range (1st, 2nd, and 3rd gears), 2 range (2nd and 3rd gears), and 1 range (1st, 2nd, and 3rd gears).

This clutch engages when the hydraulic pressure from the transmission control valve is applied to its piston, transmitting the power to the reduction drive shaft.

A cover is placed inside the piston, and the space between the piston and the cover is filled with ATF. When the low clutch is not in engagement, the centrifugal force generated in the ATF inside the cover cancels out the centrifugal force generated in the ATF remaining behind the low clutch piston, thus preventing incomplete disengagement of the clutch.

When the low clutch is engaged, the pressure pushing the clutch piston is much larger than the counteracting force of the ATF in the cover, so the clutch remains engaged.

Scheme 724

Reduction Gear

Engine torque is transmitted from the rear planetary carrier to the reduction drive shaft and the reduction drive gear. The torque is then transmitted to the front final gears through the reduction driven gear and drive pinion. The torque is also transmitted to the rear wheels from the transfer clutch hub (welded to the side of the reduction drive gear) through the transfer clutch and the following path

rear drive shaft --> propeller shaft --> rear differential.

Scheme 725

Hydraulic Control Valve

The hydraulic control system of the automatic transmission consists of an oil pump, valve bodies containing valves, clutches, fluid passages and pipes. The operation of the system is initiated by driver's manual inputs and electrical inputs from the TCM.

Scheme 726

TURBO MODELS

The structure of the control valve is simplified by disusing the accumulator and decreasing the number of mechanical valves. Disusing the accumulator and some mechanical valves allowed a two-layered body structure, which contributes to minimizing the size and weight. Also, the hydraulic control valve mechanism of the transfer duty solenoid is integrated with the control valve.

The hydraulic control system consists of an oil pump, valve bodies containing valves, clutches, fluid passages, linear solenoids, duty solenoids for each speed clutch, filters and pipes.

Oil pressure from the duty solenoid for each clutch will be directly applied to the clutch/brake without flowing through an accumulator, therefore the engagement/disengagement control range is widened and the response during gear shift is improved.

Scheme 727

Scheme 728

The gear train consists of two sets of planetary gears, three sets of multi-plate clutches, two sets of multi-plate brakes and one set of one-way clutch.

Scheme 729

Scheme 730

N RANGE

Since the rear sun gear and the high clutch drum are in mesh with the input shaft, they rotate together with the input shaft.

The high clutch drum does not transmit the torque to the planetary unit since the reverse clutch and the high clutch are not engaged.

The torque of the rear sun gear is transmitted to the rear internal gear through the pinion gear.

However, the torque of the rear sun gear is not transmitted to the rear planetary carrier since the low clutch is disengaged and, therefore, the rear internal gear is freewheeling.

As a result, the torque of the input shaft is not transmitted to the reduction drive shaft.

Scheme 731

Scheme 732

P RANGE

All the clutches and brakes are free, just as in the N range. The parking pawl engages with the parking gear which forms an integral part of the reduction drive gear, preventing the gear from rotating.

Scheme 733

Scheme 734

1st GEAR OF DOR 3 RANGE (D 1 , 3 1 )

When the 1st gear is selected in the D or 3 range, only the low clutch is engaged. In this state, the rear internal gear attempts to rotate counterclockwise but it is impossible by the action of the one-way clutch which locks the internal gear to the transmission case. As a result, rotation of the rear sun gear causes the pinion gears to rotate around the sun gear. This causes the planetary carrier to rotate. In this way, rotation of the input shaft is transmitted to the reduction drive shaft 1 after being subjected to speed reduction by the planetary gear train.

On the other hand, the rear internal gear rotates clockwise if the reverse driving force is applied to it by the reduction drive shaft 1 during coasting. This clockwise rotation of the internal gear causes the one-way clutch to freewheel. Since the power path between the reduction drive shaft 1 and the input shaft is lost as a result, no engine braking effect is available.

1. MPT models only. VTD models are equipped with an intermediate shaft.

Scheme 735

Scheme 736

2nd SPEED GEAR OF D, 3, 2 RANGE OR IN SPORTS SHIFT MODE (D2, 3 2 , 22, S2)

When the 2nd gear is selected in D, 3, 2 range or in sports shift mode, the 2-4 brake and the low clutch are engaged. The front sun gear is now locked to the transmission case due to engagement of the 2-4 brake. In this state, the torque of the rear sun gear is transmitted to the rear internal gear through the path of the front internal gear, front pinion gears, low clutch drum and low clutch. At this time, the one-way clutch is freewheeling since the low clutch drum is rotating clockwise.

In this power flow configuration, the rear pinion gears are rotated by the rear internal gear at a speed faster than that available from the configuration for the 1st gear, so the rotation speed of the reduction drive shaft 1 is higher than that of the 1st gear.

Since the drive power is transmitted without passing through the one-way clutch in the 2nd gear, the backward driving force from the wheels is transmitted through the reduction drive shaft 1 to the input shaft; this makes the engine braking effect available.

1. MPT models only. VTD models are equipped with an intermediate shaft.

Scheme 737

Scheme 738

3rd SPEED GEAR OF D, 3, RANGE OR IN SPORTS SHIFT MODE (D3, 33, S3)

When the 3rd gear is selected in the D or 3 range or in sports shift mode, the low clutch and the high clutch are engaged. The engaged high clutch rotates through its drum the front planetary carrier, and rotation of the carrier is transmitted to the rear internal gear through the engaged low clutch. In this power flow configuration, the rear sun gear and the rear internal gear rotate at the same speed since the rear pinion gears are solid on their axes and the whole planetary gear train rotates as a unit at the same speed as its sun gear. As a result, the input shaft and the reduction drive shaft rotate at the same speed.

In the 3rd gear, the one-way clutch is freewheeling because the low clutch is rotating clockwise. Since the drive power 1 is transmitted without passing through the one-way clutch, the backward driving force from the wheels is transmitted through the reduction drive shaft 1 to the input shaft; this makes the engine braking effect available.

1. MPT models only. VTD models are equipped with an intermediate shaft.

Scheme 739

Scheme 740

4th SPEED GEAR OF D RANGE OR IN SPORTS SHIFT MODE (D4, S 4 )

When the 4th gear is selected in the D range or in sports shift mode, the high clutch and the 2-4 brake are engaged. The engaged high clutch causes the front planetary carrier to rotate, whereas the engaged 2-4 brake causes the front sun gear to be locked to the transmission case.

The front planetary carrier rotates at the same speed as the input shaft. The rotation of the front planetary carrier causes the front pinion gears to revolve around the stationary front sun gear, which causes the front internal gear to rotate faster than the input shaft.

As a result, the reduction drive shaft 1 is driven at a higher speed than the input shaft.

In the 4th gear, the one-way clutch is freewheeling because the low clutch is rotating clockwise. Since the drive power is transmitted without passing through the one-way clutch, the backward driving force from the wheels is transmitted through the reduction drive shaft 1 to the input shaft; this makes the engine braking effect available.

1. MPT models only. VTD models are equipped with an intermediate shaft.

Scheme 741

Scheme 742

1st SPEED GEAR OF 1 RANGE OR IN SPORTS SHIFT MODE (11, S1)

When the 1st gear is selected in the 1 range or in sports shift mode, both the low clutch and the low & reverse brake are engaged. Although the power flow configuration is the same as that with the 1st gear in the D or 3 range, the one-way clutch produces no freewheeling effect because the low & reverse brake is locking the rear internal gear always to the transmission case.

During coasting, therefore, the backward driving force from the wheels is transmitted through the reduction drive gear 1 to the input shaft. This means, unlike the 1st gear in D or 3 range, that the engine braking effect is available in this range.

1. MPT models only. VTD models are equipped with an intermediate shaft.

Scheme 743

Scheme 744

R RANGE

When the selector lever is placed in the R position, the reverse clutch and the low & reverse brake are engaged. The reverse clutch allows the input shaft torque to be transmitted to the front sun gear, while the low & reverse brake allows the low clutch drum to be interlocked with the transmission case.

The rotation of the front sun gear causes the front pinion gear to rotate in the opposite direction and therefore the front internal gear rotates in the same direction.

At this time, the rotation speed transmitted to the front internal gear is reduced through gearing between the front sun gear and the front pinion gears.

The one-way clutch produces no freewheeling effect because the low & reverse brake is in engagement.

In this range, since the power transmission is made without passing through the one-way clutch, the driving force from the wheels is transmitted through the reduction drive shaft 1 to the input shaft; this makes the engine braking effect available.

1. MPT models only. VTD models are equipped with an intermediate shaft.

Scheme 745

Scheme 746

Scheme 747

Scheme 748

Scheme 749

Scheme 750

Scheme 751

Scheme 752

Scheme 753

Scheme 754

Scheme 755

Scheme 756

Scheme 757

Scheme 758

Scheme 759

Scheme 760

Scheme 761

Scheme 762

Scheme 763

Scheme 764

Scheme 765

Scheme 766

Scheme 767

Scheme 768

Scheme 769

Scheme 770

Scheme 771

Scheme 772

Scheme 773

Scheme 774

Scheme 775

Scheme 776

Scheme 777

Scheme 778

Scheme 779

Scheme 780

GENERAL

This all-wheel-drive (AWD) transfer system uses an electronically controlled multi-plate type transfer clutch. The clutch is controlled by the TCM through the transfer hydraulic pressure control unit which consists of a duty-cycle-controlled solenoid valve and is located at the rear of the automatic transmission section together with the vehicle speed sensor.

The TCM has in its memory a set of duty ratio data, each defining at what ratio the transfer clutch should transmit the torque for a particular driving condition. Based on the driving condition information it receives from the corresponding sensors (vehicle speed, throttle opening, gear range, slip of wheels, etc.), the TCM selects an appropriate duty ratio from the memory and uses it to control the solenoid valve. The solenoid valve then regulates the pilot pressure of the transfer control valve which creates the pressure to the clutch from the line pressure. The clutch is engaged to a degree determined by the transfer clutch pressure thus created. Through this process, the torque from the engine is distributed to the rear wheels optimally according to driving conditions.

Scheme 781

Scheme 782

Scheme 783

1. Transfer clutch The transfer clutch drum and rear drive shaft are joined to each other by welding. The rear drive shaft has drilled oil passages for transfer clutch control and also for lubrication of extension bushing and ball bearing in it.
2. Transfer hydraulic pressure control unit The transfer hydraulic pressure control unit is bolted at the rear end of transmission case through the transfer valve plate. The hydraulic pressures used for the transfer hydraulic pressure control unit (line pressure and pilot pressure) are supplied from the transmission's hydraulic control valve assembly through the passages formed in the transmission case. The transfer duty solenoid adjusts the pilot pressure of the transfer clutch valve depending on the signals from the TCM. The transfer clutch valve in turn modulates the line pressure into the transfer clutch pressure before it is applied to the clutch piston. The transfer clutch pressure adjusted in this way engages the clutch to different degrees according to driving conditions so that the optimum torque is distributed to the rear wheels.

Used in the transfer of the VTD models is the SUBARU drive power distribution system which combines a compound planetary gear type center differential installed in the transfer case behind the transmission and a hydraulically operated multi-plate differential action limiting device (LSD) located between the output components of the center differential. Differential action limiting control is performed by the TCM according to driving and road surface conditions. This system allows combining stability provided by the AWD design with good operability.

The input torque is transmitted to the 1st sun gear of the center differential through the intermediate shaft. From the 1st sun gear, the torque is transmitted through the 1st pinion to the output carrier in the front wheel output components, and through the 2nd pinion to the 2nd sun gear in the rear wheel output components.

The center differential performs the differential functions of absorbing the speed difference between the front and rear wheels and also distributes drive forces to the front and rear wheels at a predetermined ratio. In normal conditions (when there is almost no difference in the speed between the front and rear wheels), the drive force distribution ratio is 45.5 % to the front wheels and 54.5 % to the rear wheels. The hydraulic multi-plate clutch connected in parallel with the center differential between the carrier and 2nd sun gear functions as a differential action limiting device (LSD) and also as a device that controls torque distribution according to driving conditions.

The differential action limiting control is based on the parameters that include the throttle angle, engine speed, vehicle speed, and speed ratio of front and rear wheels. The LSD clutch piston is operated by the fluid whose pressure is adjusted by the duty solenoid and the transfer control valve in the transfer case. According to the pressure applied to the piston, the torque distribution ratio changes from the ratio set for the center differential to the direct AWD ratio.

The speed of the front and rear wheels determine the basic signals for the differential action limiting control. The rear wheel speed is detected by sensor installed above the rear drive shaft and the front wheel speed is detected by the sensor on the parking gear above the reduction drive shaft gear.

Scheme 784

MULTI-PLATE CLUTCH (LSD)

The transfer's differential action limiting device (LSD) consists of a multi-plate clutch and a transfer hydraulic pressure control unit incorporating a transfer duty solenoid.

The transfer duty solenoid is an electromagnetic valve which is controlled by the TCM using various duty ratios stored in its memory as explained in "1. General".

The rear drive shaft has drilled oil passages for lubrication of multi-plate clutch and extension bushing and ball bearing in it.

Scheme 785

Scheme 786

1. Non-turbo models The transfer hydraulic pressure control unit is bolted at the rear end of transmission case through the transfer valve plate. The hydraulic pressures used for the transfer hydraulic pressure control unit (line pressure and pilot pressure) are supplied from the transmission's hydraulic control valve assembly through the passages formed in the transmission case. The transfer duty solenoid adjusts the pilot pressure of the transfer control valve depending on the signals from the TCM. The transfer control valve in turn modulates the line pressure into the transfer clutch pressure before it is applied to the clutch piston. The transfer clutch pressure adjusted in this way engages the clutch to different degrees according to driving conditions so that the optimum torque is distributed to the rear wheels.
2. Turbo models The transfer hydraulic control unit is incorporated into the transmission hydraulic control valve assembly. The transfer duty solenoid adjusts the pilot pressure of the transfer control valve depending on the signals from the TCM. The transfer control valve in turn modulates the line pressure into the transfer clutch pressure before it is sent through the passages formed in the transmission case and extension case to the clutch piston. The transfer clutch pressure adjusted in this way engages the clutch to different degrees according to driving conditions so that the optimum torque is distributed to the rear wheels.

Scheme 787

Scheme 788

Scheme 789

1. Vehicles without VDC system and sports shift The electro-hydraulic control system for the transmission and transfer consists of various sensors and switches, a transmission control module (TCM) and the hydraulic controlling units including solenoid valves. The system controls the automatic transmission operation, including gear shifting, lock-up clutch operation, line pressure, automatic control pattern selection ("BASE" and "POWER"), and gear-shift timing. It also controls the operation of the transfer clutch. The TCM determines vehicle operating conditions from various input signals and controls a total of eight solenoids (shift solenoids 1 and 2, low clutch timing solenoid, 2-4 brake timing solenoid, line pressure duty solenoid, lockup duty solenoid, transfer duty solenoid, and 2-4 brake duty solenoid) by sending appropriate signals to them. NOTE: On U5 models, signals marked with "*" are transmitted over CAN communication.
2. Vehicles with VDC system The electro-hydraulic control system for the transmission and transfer consists of various sensors and switches, a transmission control module (TCM) and the hydraulic controlling units including solenoid valves. The system controls the automatic transmission operation, including gear shifting, lock-up clutch operation, line pressure, automatic control pattern selection ("BASE" and "POWER"), and gear-shift timing. It also controls operation of the transfer multi-plate clutch (LSD). The TCM determines vehicle operating conditions from various input signals and controls a total of eight solenoids (shift solenoids 1 and 2, low clutch timing solenoid, 2-4 brake timing solenoid, line pressure duty solenoid, lockup duty solenoid, transfer duty solenoid, and 2-4 brake duty solenoid) by sending appropriate signals to them.
3. Vehicles with sports shift (non-turbo models) The electro-hydraulic control system for the transmission and transfer consists of various sensors and switches, a transmission control module (TCM) and the hydraulic controlling units including solenoid valves. The system controls the automatic transmission operation, including gear shifting, lock-up clutch operation, line pressure, automatic shift pattern selection (BASE and POWER), and gear-shift timing. It also controls the operation of the transfer clutch. The TCM determines vehicle operating conditions from various input signals and controls a total of eight solenoids (shift solenoids 1 and 2, low clutch timing solenoid, 2-4 brake timing solenoid, line pressure duty solenoid, lockup duty solenoid, transfer duty solenoid, and 2-4 brake duty solenoid) by sending appropriate signals to them. A sports shift solenoid is also equipped to make engine braking effect available when 1st speed gear is selected in sports shift mode. NOTE: On U5 models, signals marked with " * " are transmitted over CAN communication.

The electro-hydraulic control system for the transmission and transfer consists of various sensors and switches, a transmission control unit and the hydraulic controlling units including solenoid valves. The system controls the automatic transmission operation, including gear shifting, lockup clutch operation, line pressure, pilot pressure, pattern selection (BASE and POWER), and gear-shift timing. It also controls the operation of the transfer clutch. The TCU determines vehicle operating conditions from various input signals and controls a total of seven solenoids (line pressure linear solenoid, lockup duty solenoid, 2-4 brake duty solenoid, low clutch duty solenoid, high clutch duty solenoid, low & reverse clutch duty solenoid, and transfer duty solenoid) by sending appropriate signals to them.

Scheme 790

Note. Signals marked with " * " are transmitted over CAN communication.

NON-TURBO MODELS

INPUT SIGNALS SPECIFICATION (NON-TURBO MODELS)

Note. Signals marked with " * " are transmitted over CAN communication.

INPUT SIGNALS SPECIFICATION (TURBO MODELS)

OUTPUT SIGNALS SPECIFICATION (NON-TURBO MODELS)

OUTPUT SIGNALS SPECIFICATION (TURBO MODELS)

MPT MODELS

LOCKUP CONTROL VALVE CONTROL ITEMS

VTD MODELS SPECIFICATION (NON-TURBO MODELS)

VTD MODELS SPECIFICATION (TURBO MODELS)

ACCELERATOR PEDAL POSITION SENSOR

The accelerator pedal position sensor provides electrical signals corresponding to accelerator pedal positions. The accelerator pedal angular position and depressing speed are detected by this accelerator pedal position sensor. (turbo models)

THROTTLE POSITION SENSOR

The throttle position sensor provides electrical signals corresponding to throttle valve positions. The throttle valve angular position and accelerator pedal depressing speed are detected by this throttle position sensor. (non-turbo models)

This vehicle speed sensor (output shaft speed sensor) is externally mounted on the extension case. It detects the rear wheel speed in terms of the peripheral speed of the transfer clutch drum and sends sine wave signals (30 pulses per rotation) to the TCM.

Scheme 791

Scheme 792

Scheme 793

1. Non-turbo models This vehicle speed sensor (output shaft speed sensor) is externally mounted on the extension case. It detects the rear wheel speed in terms of the peripheral speed of the rear drive shaft and sends sine wave signals (22 pulses per rotation) to the TCM.
2. Turbo models This vehicle speed sensor (output shaft speed sensor) is a Hall element type sensor and is externally mounted on the extension case. It detects the rear wheel speed in terms of the peripheral speed of the rear drive shaft and sends pulse signals (22 pulses per rotation) to the TCM.

FRONT VEHICLE SPEED SENSOR

This vehicle speed sensor (output shaft speed sensor) is externally mounted on the transmission case. It detects the front wheel speed and sends sine wave signals (16 pulses per rotation) to the TCM.

The TCM converts the signals into pulse signals and outputs them to both the engine control module (ECM) and the combination meter.

Scheme 794

Scheme 795

1. MPT models
2. VTD models

ATF TEMPERATURE SENSOR

This sensor is mounted on the hydraulic control valve body of the transmission. It detects the temperature of ATF and outputs it as an electrical resistance signal. The output characteristics of the sensor are shown below.

Scheme 796

Scheme 797

1. Non-turbo models
2. Turbo models

INHIBITOR SWITCH

The inhibitor switch assures safety when starting the engine. This switch is mounted on the right side of the transmission case, and is operated by the selector lever.

When the selector lever is set to P or N, the electrical circuit in the inhibitor switch is closed and the starter circuit is completed for cranking the engine.

When the selector lever is in the R, D, 3, 2 or 1 range, the electrical circuit in the inhibitor switch is open. Hence engine cranking is disabled. In the R range, the backup light circuit is completed in the switch, and the backup lights come on.

In addition to the above function, the inhibitor switch incorporates a circuit for detecting the selected range position and sending the range signal to the TCM.

Inhibitor switch side connector

Scheme 798

RANGE POSITION SPECIFICATION

SHIFT SOLENOIDS 1 AND 2

These solenoids are mounted on the transmission hydraulic control valve body. They are turned ON or OFF according to signals from the TCM. The gear positions are changed according to the ON and OFF condition of these solenoids.

Scheme 799

LOW-CLUTCH TIMING SOLENOID

This solenoid is mounted on the transmission hydraulic control valve body. It is turned ON or OFF according to signals from the TCM. It then controls the low clutch timing valve B and reverse inhibitor valve.

Scheme 800

2-4 BRAKE TIMING SOLENOID

This solenoid is mounted on the transmission hydraulic control valve body. It is turned ON or OFF according to signals from the TCM. It then controls the 2-4 brake timing valve B to decrease the change gear shock.

Scheme 801

LINE PRESSURE DUTY SOLENOID

This solenoid is mounted on the transmission hydraulic control valve body. Its duty ratio is controlled by signals from the TCM. This solenoid then controls the pressure modifier valve and accumulator control valve A to adjust the line pressure to an optimum pressure level suitable for operating conditions.

Scheme 802

LOCKUP DUTY SOLENOID

This solenoid is mounted on the transmission hydraulic control valve body. Its duty ratio is controlled by signals from the TCM. It then controls the lock-up control valve to provide smooth engagement and disengagement of the lock-up clutch.

Scheme 803

2-4 BRAKE DUTY SOLENOID

This solenoid is mounted on the transmission hydraulic control valve body. Its duty ratio is controlled by signals from the TCM. It modulates the 2-4 brake pressure when the 2-4 brake is operated, reducing shifting shocks.

Scheme 804

This solenoid is mounted on the transfer hydraulic pressure control unit on the rear end of transmission case. Its duty ratio is controlled by signals from the TCM. It then controls the transfer clutch/control valve to control the pressure applied to the transfer clutch.

Scheme 805

Scheme 806

1. MPT models
2. VTD models

This solenoid is mounted on the transmission hydraulic control valve. Its duty ratio is controlled by signals from the TCM. It then regulates the pressure applied to the transfer clutch to control the drive power distributed to the front and rear wheels.

Scheme 807

SPORTS SHIFT SOLENOID

This solenoid is mounted on the transmission hydraulic control valve body. It is turned ON or OFF according to signals from the TCM. Thus the sports shift control valve is controlled when 1st speed gear is selected in sports shift mode, (non-turbo models)

Scheme 808

LINE PRESSURE LINEAR SOLENOID

This solenoid is mounted on the transmission hydraulic control valve. Its duty ratio is controlled by signals from the TCM. The line pressure is regulated to an optimum level according to the driving condition.

Scheme 809

This solenoid is mounted on the transmission hydraulic control valve. Its duty ratio is controlled by signals from the TCM. It modulates the pressure applied to the 2-4 brake pressure when the 2-4 brake is operated to reduce shifting shocks.

Scheme 810

This solenoid is mounted on the transmission hydraulic control valve. Its duty ratio is controlled by signals from the TCM. The solenoid provides smooth engagement and disengagement of the lockup clutch.

Scheme 811

LOW CLUTCH DUTY SOLENOID

This solenoid is mounted on the transmission hydraulic control valve. Its duty ratio is controlled by signals from the TCM. It modulates the pressure applied to the low clutch when the low clutch is operated to reduce shifting shocks.

Scheme 812

HIGH CLUTCH DUTY SOLENOID

This solenoid is mounted on the transmission hydraulic control valve. Its duty ratio is controlled by signals from the TCM. It modulates the pressure applied to the high clutch when the high clutch is operated to reduce shifting shocks.

Scheme 813

LOW & REVERSE BRAKE DUTY SOLENOID

This solenoid is mounted on the transmission hydraulic control valve. Its duty ratio is controlled by signals from the TCM. It modulates the pressure applied to the low & reverse brake when the low & reverse brake is operated to reduce shifting shocks.

Scheme 814

Transmission Control Module (TCM)

The TCM receives various sensor signals and determines the running conditions of the vehicle. It then sends control signals to each solenoid according to the preset gearshift characteristic data, lock-up operation data, and transfer clutch torque data (duty ratios).

MPT MODELS SPECIFICATION

VTD MODELS SPECIFICATION

VTD MODELS SPECIFICATION

VTD MODELS SPECIFICATION

Scheme 815

Scheme 816

The TCM performs gear shifting control according to driving conditions by using the shift point characteristic data stored in its memory. Appropriate solenoids are operated at the proper timing corresponding to the shift pattern, throttle position, and vehicle speed for smooth shifting.

Note. When the ATF temperature is below approximately -10°C (-50°F), the gear cannot be shifted to 4th speed.

SOLENOID SPECIFICATION

Scheme 817

Scheme 818

1. The TCM activates both solenoids 1 and 2 in response to throttle and vehicle speed signals.
2. Shift valves move in response to operation of the solenoids, supplying or interrupting the line pressure to each clutch.
3. A shift to each gear takes place according to ON-OFF operation of both the solenoids as indicated in the table above.

The TCM performs gear shifting control according to driving conditions by using the shift point characteristic data stored in its memory. Appropriate duty solenoids are operated at the proper timing corresponding to the shift pattern, throttle position, and vehicle speed for smooth shifting.

Note. When the ATF temperature is below approximately -10°C (-50°F), the gear cannot be shifted to 4th speed.

Scheme 819

1. The TCM activates each duty solenoid in response to throttle opening and vehicle speed signals.
2. According to the operation of the duty solenoids, the line pressure to each clutch and brake is supplied or interrupted.

LOCKUP CONTROL

1. The TCM has pre-programmed lockup clutch engagement and disengagement conditions for each gear and shift pattern. The engagement and disengagement conditions are defined in terms of the throttle valve position and vehicle speed.
2. The TCM controls the operation of the lockup clutch by means of the duty solenoid which in turn controls the lockup control valve as described below

The line pressure which engages shift clutches to create 1st to 4th speeds is controlled by the TCM to meet varying operating conditions.

During gear shifting, the TCM decreases the line pressure to a level that matches the selected gear in order to minimize shifting shock loads.

Scheme 820

During gear shifting, the TCM controls the line pressure as follows

1. The TCM receives signals such as throttle position signal and accelerator pedal speed signal. Based on these input signals, it issues a control signal to the line pressure duty solenoid.
2. The pressure from the line pressure duty solenoid (line pressure duty pressure) is converted by the pressure modifier valve into a modifier pressure, and the modifier pressure is applied to the pressure regulator valve.
3. The pressure regulator valve adjusts the oil-pump-generated line pressure according to the modifier pressure to make the line pressure matched to the driving condition.

The line pressure which engages shift clutches to create 1st to 4th speeds is controlled by the TCM to meet varying operating conditions.

1. The TCM receives signals such as throttle position signal and accelerator pedal speed signal. Based on these input signals, it issues a control signal to the line pressure linear solenoid.
2. The pressure from the line pressure duty solenoid is sent to the valve where the line pressure is regulated. The valve adjusts the oil-pump-generated line pressure to make the line pressure matched to the driving condition.

SHIFT PATTERN SELECTION CONTROL

The TCM changes its gear shift control pattern automatically between the BASE pattern suitable for ordinary economy driving and the POWER pattern suitable for climbing uphill or rapid acceleration.

In the POWER pattern, the downshift point and upshift point are set higher than those of the BASE pattern.

SELECTOR LEVER POSITION SPECIFICATION

Scheme 821

GRADE CONTROL

While the vehicle is driving up a hill, the gear is fixed to the 3rd to avoid repeated gear shift between the 3rd and 4th gears.

When the vehicle is descending a steep slope at a speed of approximately 80 km/hour (50 miles/hour), a 4th to 3rd downshift occurs automatically when the brake pedal is depressed. This gearshift control is cancelled when the accelerator pedal is depressed.

The TCM performs these controls based mainly on the throttle opening, engine speed and vehicle speed.

Scheme 822

Scheme 823

LEARNING CONTROL

The TCM has a learning control function with which it can adapt gear shift timing optimally to the current vehicle conditions by updating correction factors in the memory.

For this reason, gear shift shock may become larger after the power supply is interrupted (disconnection of battery, flat battery, etc.) or immediately after the ATF is replaced.

Larger gear shift shock after power supply interruption occurs because the correction data is reset to those for the new vehicle condition, (non-turbo models)

The TCM starts learning function again as soon as the power supply is restored. After driving for a while, therefore, the transmission will become able to make gearshifts at the optimum timing. Larger shift shock immediately after ATF change is caused by change in friction characteristics of the transmission internal parts. Also in this case, the transmission recovers shock-less gear shifting after driving for a while.

REVERSE INHIBITION CONTROL

Note. This control is performed on non-turbo models only.

This control prevents the transmission from shifting into the reverse gear when the select lever is accidentally placed in the R position, thus protecting the components such as reverse clutch from being damaged.

If the selector lever is moved to the R position during driving at a speed faster than the predetermined speed, the low clutch timing solenoid is energized. Then, the pilot pressure is supplied to the reverse inhibitor valve. This causes the reverse inhibitor valve to move downward, closing the low & reverse brake port.

In this condition, the low & reverse brake does not engage since the ATF flowing from the manual valve is blocked by the reverse inhibitor valve.

As a result, the transmission is put into the neutral state, and the shifting into the reverse gear is inhibited.

Scheme 824

Scheme 825

Scheme 826

1 RANGE CONTROL

RANGE CONTROL SPECIFICATION

SLIP CONTROL

SLIP CONTROL SPECIFICATION

TURNING CONTROL

TURNING CONTROL SPECIFICATION

ABS CONTROL

ABS CONTROL SPECIFICATION

P AND N RANGE CONTROL

P AND N RANGE CONTROL SPECIFICATION

FLOW CONTROL

The torque input to the multi-plate clutch is calculated according to various factors such as intake manifold pressure, torque converter turbine speed and selected speed gear. Based on the calculation result, the basic coupling force of the clutch is determined.

The basic coupling force thus obtained is then corrected according to the road slipperiness (which is determined based on steering angle, yaw rate, lateral G signals from the VDC control module) and the feedback correction factor which is used for making the actual yaw rate agree with the yaw rate estimated from the steering angle sensor signals, (models with VDC)

START CONTROL

When the vehicle speed is 0 km/h (0 MPH), the TCM makes control to generate differential action limiting torque that is proportional to the throttle angle.

This enables the vehicle to start smoothly without swerving even on a slippery road.

The TCM makes a correction such that the input torque to the multi-plate clutch is reduced as the steering angle increases.

This function is performed to improves turning performance at certain vehicle speed range.

When front or rear wheels start slipping with the vehicle running slower than the predetermined speed, the TCM makes control to increase the differential action limiting torque.

This function maintains traction and improves driving stability.

Scheme 827

When the TCM receives an ABS operation signal from the ABS unit, it adjusts the differential action limiting torque to the predetermined level and selects a gear speed appropriate for the vehicle speed.

This function improves ABS control.

BASE BRAKE CONTROL

When the brake switch is ON and the throttle valve is fully closed, the TCM makes control to decrease the differential action limiting torque. The ABS control has priority over this control.

This function improves stability during braking.

When the 1 range is selected, the TCM makes control to increase the differential action limiting torque.

This function improves driving performance and traction.

CONTROL SYSTEM

The TCM is constantly monitoring the driving conditions of the vehicle using the eleven input signals. Based on the conditions it has determined, the TCM adjusts the duty ratio of current to the transfer duty solenoid thus changing the engagement of the multi-plate clutch. The input signals are used also for automatic transmission control.

Scheme 828

The transfer hydraulic pressure control unit includes a valve body attached to the side of the extension case through a gasket and separator plate.

The pressurized fluids for the transfer hydraulic control (line pressure and pilot pressure) are supplied from the oil pump by way of the passages formed in the transmission case and then the passages in the extension case that lead to the hydraulic circuit in the transfer valve body.

The line pressure is regulated by the transfer control valve whose opening is controlled by the transfer pressure created by the transfer duty solenoid.

1. The transfer duty solenoid is controlled by the TCM. The TCM changes the solenoid controlling duty ratio according to driving conditions.
2. The transfer duty solenoid creates the transfer pressure from the pilot pressure. The transfer pressure is applied to the transfer control valve and adjusts the valve's opening.
3. The line pressure directly led to the transfer control valve, on the other hand, is regulated by the transfer control valve and becomes the transfer clutch pressure.
4. The transfer clutch pressure is applied to the transfer clutch and engages the clutch to a controlled degree.

In this way, the degree of transfer clutch engagement is varied so that optimum torque is distributed to the rear wheels according to vehicle driving conditions.

Scheme 829

VTD MODELS

The drive power distribution system includes a valve body attached to the side of the extension case through a gasket and separator plate.

Pressurized fluids for the drive power distribution system (line pressure and pilot pressure) are supplied from the oil pump by way of the passages formed in the transmission case and then the passages in the extension case that lead to the hydraulic circuit in the transfer valve body.

The line pressure is regulated by the transfer control valve whose opening is controlled by the transfer pressure created by the transfer duty solenoid.

1. The pilot pressure created by passing through the pilot valve in the transmission's hydraulic control assembly is further regulated into the transfer pressure by the transfer duty solenoid.
2. The transfer duty solenoid is controlled by the TCM. The TCM changes the solenoid controlling duty ratio according to driving conditions.
3. The transfer pressure thus created is applied to the transfer control valve and adjusts the valve's opening.
4. The line pressure directly led to the transfer control valve, on the other hand, is regulated by the transfer control valve and becomes the transfer clutch pressure.
5. The transfer clutch pressure is applied to the multi-plate clutch (LSD) and engages the clutch to a controlled degree.

In this way, the degree of multi-plate clutch engagement is varied so that optimum torque is distributed to the rear wheels.

Scheme 830

SPORTS SHIFT CONTROL

When the select lever is moved to the sports shift gate side, the TCM interprets this as the shift pattern is switched to the sports shift mode. In this state, moving the select lever forward ("+" direction) will cause an upshift and moving the lever rearward ("-" direction) will cause a downshift to occur. However, if there is a possibility of the engine speed to go out of the preset shifting range, the following control is performed.

1. Upshift inhibiting and auto downshift control The gear upshifts from 1st to 4th speed, one by one for each time the select lever is moved forward (+ direction). However, when the vehicle speed is too low for the gear speed, the TCM inhibits further upshifting. If the vehicle speed becomes even slower, a downshift will be made to prevent engine stall. When the vehicle comes to a stop, the transmission will always be controlled to shift to 1st speed.
2. Downshift inhibiting control The gear downshifts from 4th to 1st speed, one by one for each time the select lever is moved rearward (- direction). However, when the vehicle speed is too high for the gear speed, the TCM inhibits further downshifting. A buzzer will sound to warn the driver.
3. If the engine speed exceeds the preset value during accelerating, the fuel supply is cut to prevent over-revving of the engine.

N-R LOCK CONTROL

Note. This control is performed on DOHC turbo models.

This control prevents the select lever from being moved to the R position when the vehicle is running. Thus damage to components such as the reverse clutch is prevented.

When the specified speed is exceeded the TCM turns off the shift lock solenoid for the select lever. Therefore the N-R mechanism works to inhibit operation from N range to R range, preventing the transmission from being reversed.

The on-board diagnostics system detects and stores in the form of a code a fault that has occurred in any of the following input and output signal systems.

FUNCTION SPECIFICATION (NON-TURBO MODELS)

If a fault has been detected, the system tells the fault by causing the AT OIL TEMP warning light to operate as follows

1. Repeated flashing at 4 Hz frequency...Errors such as battery trouble
2. Repeated flashing at 2 Hz frequency...No faults in the system
3. Flashing at different intervals and frequencies...Diagnostic trouble codes of corresponding faults
4. Continued illumination of light...Fault in inhibitor switch, idle switch, or wiring

The on-board diagnostics system detects a fault that has occurred in any of the following input and output signal systems.

FUNCTION SPECIFICATION (TURBO MODELS)

DTCs are checked by reading them with a select monitor.

DIAGNOSTIC TROUBLE CODES

SELECT MONITOR

Various sensor and switch data as well as diagnostic trouble codes for faults that are currently present and occurred in the past can be monitored by connecting the select monitor to the select monitor terminal located under the instrument panel.

The fail-safe control function ensures minimum level of driveability even if a fault should occur in the vehicle speed sensors, throttle position sensor, inhibitor switch, or any of the solenoids.

1. Front and rear vehicle speed sensors A dual speed-sensing system is used. The speed signal is taken from the transmission (by the output shaft speed sensor). Even if one sensor system fails, the vehicle can be controlled normally with the other normally operating sensor system. If both the front and rear vehicle speed sensors become faulty, the vehicle is made to operate only in the 3rd speed.
2. Throttle position sensor If the throttle position sensor becomes faulty, the throttle opening is fixed at the predetermined angle.
3. Inhibitor switch If the TCM receives different signals simultaneously from a faulty inhibitor switch, it selects a range in the following priority: D > 3 > 2 > 1 > R > N, P
4. Shift solenoid 1 and 2 If a fault occurs in either of solenoids 1 and 2, both the solenoids are de-energized, and the gear is held in the 3rd. If both the solenoids should fail, the TCM invariably selects and keeps the 3rd gear.
5. Line pressure duty solenoid If the line pressure duty solenoid fails, the solenoid is de-energized and the line pressure is raised to the maximum to enable the vehicle to operate. In this condition, the usable gears are limited to the 1st and 3rd.
6. Lockup duty solenoid If the lockup duty solenoid fails, the solenoid is de-energized and the lockup clutch is disengaged.
7. Transfer duty solenoid When the transfer duty solenoid becomes faulty, it is de-energized. This causes oil pressure to the transfer clutch to be interrupted and no power is transmitted to the rear axle (FWD state).
8. 2-4 brake duty solenoid If a fault occurs in the 2-4 brake duty solenoid, the solenoid is de-energized and the usable gears are limited to the 1st and 3rd.
9. Low-clutch timing solenoid If a fault occurs in the low clutch timing solenoid, the solenoid is de-energized and the usable gears are limited to the 1st and 3rd.
10. 2-4 brake timing solenoid If a fault occurs in the 2-4 brake timing solenoid, the solenoid is de-energized and the usable gears are limited to the 1st and 3rd.
11. Torque converter turbine speed sensor If a fault occurs in the torque converter turbine speed sensor, the usable gears are limited to the 1st and 3rd.

The fail-safe control function ensures minimum level of driveability even if a fault should occur in the vehicle speed sensors, throttle position sensor, inhibitor switch, or any of the solenoids.

1. Front and rear vehicle speed sensors A dual speed-sensing system is used. The speed signal is taken from the transmission (by the output shaft speed sensor). Even if one sensor system fails, the vehicle can be controlled normally with the other normally operating sensor system. If both the front and rear vehicle speed sensors become faulty, the vehicle is made to operate only in the 3rd speed.
2. Throttle position sensor If the throttle position sensor becomes faulty, control will be maintained by assuming that the throttle opening is at a certain angle.
3. Inhibitor switch If the TCM receives different signals simultaneously from a faulty inhibitor switch, it selects a range in the following priority: D > N (P) > R > 3 > 2 > 1 >
4. Line pressure linear solenoid If the line pressure linear solenoid fails, the solenoid is de-energized and the line pressure is raised to the maximum to enable the vehicle to operate.
5. Lockup duty solenoid If the lockup duty solenoid fails, the solenoid is de-energized and the lockup clutch is disengaged.
6. Transfer duty solenoid When the transfer duty solenoid becomes faulty, it is de-energized. This causes oil pressure to the transfer clutch to be interrupted and no power is transmitted to the rear axle (FWD state).
7. 2-4 brake duty solenoid If a fault occurs in the 2-4 brake duty solenoid, the solenoid is de-energized and the gears are limited to the 1st and 3rd.
8. Low clutch duty solenoid If a fault occurs in the low clutch duty solenoid, the solenoid is de-energized and the gears are limited to the 1st and 3rd.
9. High clutch duty solenoid If a fault occurs in the high clutch duty solenoid, the solenoid is de-energized and the gears are limited to the 1st and 3rd.
10. Torque converter turbine speed sensor If a fault occurs in the torque converter turbine speed sensor, the gears are limited to the 3rd speed.
11. Low & reverse duty solenoid If a fault occurs in the low and reverse duty solenoid, the solenoid is de-energized and the gears are limited to the 1st.

The transmission mounting consists of a pitching stopper, cushion rubber, and a cross member.

In addition to support the transmission, these components absorb noise and vibration caused by the transmission.

Scheme 831