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 703
Scheme 704
- 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 through the oil pump housing and oil pump cover, it enters the suction port.
- 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 discharged port.
- 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.
- As engine speed increases, the delivery rate of the oil pump also increases.
Scheme 705
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 706
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 707
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's 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 708
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 709
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 710
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 clutch to lock.
The low clutch consists of a drum, a piston, return springs, a cover, drive plates, driven plates, a 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 711
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 712
REDUCTION GEARS
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 the reduction drive gear) through the transfer clutch and the following path
Rear drive shaft --> propeller shaft --> rear differential.
Scheme 713
HYDRAULIC CONTROL VALVE
The hydraulic control system of the automatic transmission consists or 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 electric inputs from the TCM.
Scheme 714
Scheme 715
Scheme 716
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 717
Scheme 718
N RANGE
Since the rear sun gear 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*.
Note. *: MPT models only. VTD models are equipped with an intermediate shaft.
Scheme 719
Scheme 720
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 721
Scheme 722
3RD GEAR OF D OR 3 RANGE (D 1 , 1 3 )
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* 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* 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* and the input shaft is lost as a result, no engine braking effect is available.
Note. *: MPT models only. VTD models are equipped with an intermediate shaft.
Scheme 723
Scheme 724
2ND GEAR OF D, 3 OR 2 RANGE (D 2 , 3 2 , 2 2 )
When the 2nd gear is selected in the D, 3 or 2 range, 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* 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* to the input shaft; this makes the engine braking effect available.
Note. *: MPT models only. VTD models are equipped with an intermediate shaft.
Scheme 725
Scheme 726
3RD GEAR OF D OR 3 RANGE (D 3 , 3 3 )
When the 3rd gear is selected in the D or 3 range, 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 is transmitted without passing through the one-way clutch, the backward driving force from the wheels is transmitted through the reduction drive shaft* to the input shaft; this makes the engine braking effect available.
Note. *: MPT models only. VTD models are equipped with an intermediate shaft.
Scheme 727
Scheme 728
4TH GEAR OF D RANGE (D 4 )
When the 4th gear is selected in the D range, 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* 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* to the input shaft; this makes the engine braking effect available.
Note. *: MPT models only. VTD models are equipped with an intermediate shaft.
Scheme 729
Scheme 730
1ST SPEED GEAR OF 1 RANGE (1 1 )
When the 1st gear is selected in the 1 range, both the low clutch and the low & reverse brake are engaged. Although the power flow configuration is the same as the 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* 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.
Note. *: MPT models only. VTD models are equipped with an intermediate shaft.
Scheme 731
Scheme 732
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* to the input shaft; this makes the engine braking effect available.
Note. *: MPT models only. VTD models are equipped with an intermediate shaft.
Scheme 733
Scheme 734
Scheme 735
Scheme 736
Scheme 737
Scheme 738
Scheme 739
Scheme 740
Scheme 741
Scheme 742
Scheme 743
Scheme 744
Scheme 745
Scheme 746
Scheme 747
Scheme 748
Scheme 749
Scheme 750
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 751
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.
Scheme 752
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.
Scheme 753
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 754
VARIABLE TORQUE DISTRIBUTION CENTER DIFFERENTIAL
The front-rear torque distribution ratio is basically determined by the gear tooth ratio of center differential's compound planetary gears and varied by changing the degree of engagement of the hydraulically operated multi-plate clutch that connects the center differential output elements according to driving conditions and road surface conditions. The torque distribution ratio is calculated using the following equations which include torque distribution coefficients (determined by number of gear teeth), input torque to the center differential, and torque capacity of the multi-plate clutch as factors.
Scheme 755
Scheme 756
Scheme 757
Scheme 758
- When the front wheel speed is higher than the rear wheel speed: T R = 0.545 X T i + T C T F = 0.455 X T i - T C where T R : Rear wheel output torque T i : Input torque to center differential T C : Torque capacity of multi-plate clutch T F : Front wheel output torque 0.545: Coefficient of rear wheel torque determined by number of gear teeth 0.455: Coefficient of front wheel torque determined by number of gear teeth
- When the rear wheel speed is higher than the front wheel speed: T R = 0.545 X T i - T C T F = 0.455 X T i + T C < Calculation of front and rear wheel torques> If the frictional resistance resulting from meshing of the planetary gears and sliding of rotational components are ignored, the torques distributed to the front and rear wheels are expressed by the following equations: T R = [(Z P1 X Z S2 ) / (Z S1 X Z P2 )] X T i T F = [1 - (Z P1 X Z S2 ) / (Z S1 X Z P2 )] X T i where Z P1 : Number of teeth of 1st planetary gear Z P2 : Number of teeth of 2nd planetary gear Z S1 : Number of teeth of 1st sun gear Z S2 : Number of teeth of 2nd sun gear T i : Input torque If the number of teeth in each component in each component is the same as that assumed in the equations on the previous page, the following ratios are the calculation results of the equations shown above. T R = 0.545 X T i T F = 0.455 X T i As a result, the front-rear torque distribution ratio of the compound planetary gear set without an adjustment by the multi-plate clutch is 45.5 : 54.5.
CENTER DIFFERENTIAL ASSEMBLY
The center differential is a compound planetary gear set without internally-toothed gears. The input torque from the automatic transmission is transmitted to the input element of the center differential (1st sun gear). The front wheel output elements of the center differential are connected to the carrier and the rear wheel output elements are connected to the 2nd sun gear.
The compound planetary gears uses helical gears for quiet operation and strength. The three pinions are arranged to ensure the best motion balance during operation.
Scheme 759
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 760
5. TRANSFER HYDRAULIC PRESSURE CONTROL UNIT
The transfer hydraulic pressure control unit is bolted at the rear and 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.
Scheme 761
DESCRIPTION
The electrohydraulic 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, lock-up duty solenoid, transfer duty solenoid, and 2-4 brake duty solenoid) by sending appropriate signals to them.
Scheme 762
Scheme 763
Scheme 764
Scheme 765
THROTTLE POSITION SENSOR
The throttle position sensor provides electrical signals corresponding to throttle valve positions. The throttle valve angular position and accelerator depressing speed are detected by this throttle position sensor.
MPT 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 766
VTD 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.
Scheme 767
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 768
Scheme 769
ATF TEMPERATURE SENSOR
This sensor is integrated with the transmission harness and 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 770
TORQUE CONVERTER TURBINE SPEED SENSOR
The torque converter turbine speed sensor (output shaft speed sensor) is externally mounted on the transmission case.
The sensor detects the torque converter turbine speed in terms of the rotation speed of the periphery of the high clutch drum coupled to the input shaft, and sends sine wave signals (32 pulses per rotation) to the TCM. The TCM calculates the proportion of the input shaft speed to the vehicle speed and determines whether the shifting is to be made or not.
Scheme 771
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.
Scheme 772
Scheme 773
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 774
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 775
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 776
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 777
LOCK-UP 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 778
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 779
TRANSFER DUTY SOLENOID
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 780
Scheme 781
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).
Scheme 782
Scheme 783
Scheme 784
Scheme 785
SHIFTING CONTROL
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.
Scheme 786
Scheme 787
- The TCM activates both solenoids 1 and 2 in response to throttle and vehicle speed signals.
- Shift valves move in response to operation of the solenoids, supplying or interrupting the line pressure to each clutch.
- A shift to each gear takes place according to ON-OFF operation of both the solenoids as indicated in the table above. (Scheme 786)
LOCK-UP CONTROL
- The TCM has pre-programmed lock-up clutch engagement and disengagement conditions for each gear and shift pattern. In addition, it specifies engagement of the clutch whenever the 4th gear is selected in the D range. The engagement and disengagement conditions are defined in terms of the throttle valve position and vehicle speed.
- The TCM controls the operation of the lock-up clutch by means of the duty solenoid which in turn controls the lock-up control valve as described below
NON-LOCK-UP OPERATION
The duty solenoid allows the pilot pressure (supplied from the pilot valve) to be applied to the "disengaging" end of the lock-up control valve spool. The lock-up control valve then opens the clutch disengaging circuit port to allow the lock-up operating pressure (torque converter clutch regular pressure) to build up in the circuit. On the other hand, the valve opens the clutch engaging circuit's port and allows the fluid in the circuit to flow to the ATF cooler, thus lowering the pressure in the circuit. As a result, the lock-up clutch is disengaged due to difference in pressure between both circuits.
This operation is performed for all the speed gears except the 4th gear of the D range.
LOCK-UP OPERATION
The duty solenoid allows the pilot pressure to be applied to the "engaging" end of the lock-up control valve spool. The lock-up control valve then opens the clutch engaging circuit's port that communicates to the torque converter's impeller chamber, allowing high pressure fluid to flow to the lock-up clutch. The clutch then engages.
- The TCM controls the current to the duty solenoid by gradually changing the current. As a result, the lock-up control valve also moves gradually, so the clutch engagement pressure increases smoothly. This causes the lock-up clutch to become initially in a half-engaged state and then in a fully engaged state, thus preventing shock during engagement.
This operation is performed for all the speed gears and always when the 4th gear is selected in the D range.
Scheme 788
- The oil pump delivery pressure (line pressure) is regulated to a constant pressure by the pilot valve. This pressure is used as the pilot pressure for controlling spool valves.
- The pilot pressure applied to the pressure modifier valve is modulated into pressure modifier pressure at the line pressure duty solenoid by activating the pressure modifier valve.
- The pressure modifier valve is an auxiliary valve for the pressure regulator valve, and it creates a signal pressure (pressure modifier pressure). The pressure modifier pressure is used to regulate the line pressure to a level optimum for a particular driving condition.
- This pressure modifier pressure is applied to the pressure regulator valve which controls the oil pump delivery pressure.
- The pressure modifier pressure from the pressure modifier valve is cushioned by the pressure modifier accumulator to remove pulsation of the pressure.
LINE-PRESSURE CONTROL DURING SHIFTING
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 789
During gear shifting, the TCM controls the line pressure as follows
- 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.
- 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.
- 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.
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.
Scheme 790
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/h (50 MPH), 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 791
Scheme 792
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.
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 gear shifts 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 shockless gear shifting after driving for a while.
REVERSE INHIBITION CONTROL
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 793
Scheme 794
Scheme 795
Scheme 796
Scheme 797
Scheme 798
Scheme 799
Scheme 800
CONTROL DESCRIPTION
The TCM controls the engagement of the center differential's multi-plate clutch (LSD) using maps that are pre-programmed based on the throttle opening and engine speed. It selects a map according to driving conditions and use it as the control basis.
ORDINARY CONTROL
A specific map is given to each of the 1st to 4th gears and the reverse gear for use by the TCM to control the torque distribution appropriately during ordinary driving conditions.
The maps are programmed in such a way that the differential action limiting torque decreases as the throttle valve opening decreases and as the vehicle speed increases. This way of control is employed in order to reduce internal circulation of torque and also to improve steering performance and stability of the vehicle's behavior when the accelerator pedal is released or when a downshift is performed, thus upgrading the stability achieved by the AWD system.
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.
TURNING CONTROL
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.
SLIP CONTROL
When front or rear wheels start slipping with the vehicle running slower than the predetermined speed, the TCM makes control is increase the differential action limiting torque.
This function maintains traction and improves driving stability.
Scheme 801
ABC-IN-OPERATION CONTROL
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 the 3rd gear in which the one-way clutch is freewheeling.
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.
1 RANGE CONTROL
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 802
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 pressure 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.
Scheme 803
- The transfer duty solenoid is controlled by the TCM. The TCM changes the solenoid controlling duty ratio according to driving conditions.
- 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.
- 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.
- 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.
The drive power distribution system includes a valve body attached to the side of the extension case through a gasket and separator plate.
The 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.
Scheme 804
- 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.
- The transfer duty solenoid is controlled by the TCM. The TCM changes the solenoid controlling duty ratio according to driving conditions.
- The transfer pressure thus created is applied to the transfer control valve and adjusts the valve's opening.
- 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.
- 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
The on-board diagnostics system detects and store in the form of a code a fault that has occurred in any of the following input and output signal systems.
Scheme 805
If a fault has been detected, the system tells the fault by causing the AT OIL TEMP warning light to operate as follows
- Repeated flashing at 4 Hz frequency ...Errors such as battery trouble
- Repeated flashing at 2 Hz frequency ...No faults in the system
- Flashing at different intervals and frequencies ...Diagnostic trouble codes of corresponding faults
- Continued illumination of light ...Fault in wiring
OPERATION OF AT OIL TEMP WARNING LIGHT
On starting the engine, the AT OIL TEMP warning light illuminates and then goes out as shown in the "Normal" diagram below. If any problem exists, the light continues flashing as shown in the "Abnormal" diagram below.
Scheme 806
Scheme 807
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.
FAIL-SAFE FUNCTION
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.
- Front and rear vehicle speed sensors A dual speed-sensing system is used. The speed signal is taken from the transmission (by the out-put 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 1st and 3rd speeds.
- Throttle position sensor If the throttle position sensor becomes faulty, the throttle opening is fixed at the predetermined angle.
- 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 >
- 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.
- Line pressure duty solenoid. If the line pressure duty solenoid fails, the solenoid is de-energized 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.
- Lock-up duty solenoid If the lock-up duty solenoid fails, the solenoid is de-energized and the lock-up clutch is disengaged.
- Transfer duty solenoid When the transfer duty solenoid becomes faulty, it is de-energized. This causes maximum oil pressure to be applied to the transfer clutch so that the power is always transmitted to the rear axle (direct-coupled AWD condition).
- 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.
- 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.
- 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.
- 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 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.
