Component Description

Introduction





This electronically controlled five speed unit is unique to supercharged vehicles.

Components and Functions

Torque converter
This assembly acts as a fluid coupling between the engine and transmission and provides multiplication of engine torque. It also allows speed and torque adaption when starting from rest.
It comprises of the following components:
Housing, impeller, turbine, stator, freewheel and a lock up clutch assembly.
The lock-up clutch reduces converter slip and so, engine speed. Depending on engine speed and load, the clutch is engaged automatically, normally in 4th and 5th gears.
The converter is fitted with a drain plug.

Transmission casing
The following components are housed within the casing;
Stator, intermediate and output shafts.
Three epicyclic geartrains.
Six multi-disc clutch/brake packs.
Two freewheels (One-way clutches).
Hydraulic pump.
Parking lock assembly.
Electro-hydraulic control unit.
Internal harness and 13 pin connector with bayonet lock.

Power flow through the transmission
From the Torque converter, power is transferred to the three epicyclic geartrains, various elements of which can either be joined together or held still by either the Freewheels or the Multi-disc Clutch/Brake assemblies (controlled by the Electro-hydraulic control unit). This combination of elements results in five forward and two reverse gear ratios. The resulting rotational torque is taken from the transmission output shaft, to the final drive assembly via the driveshaft.

Hydraulic pump
This engine driven pump is located at the front of the transmission casing and provides pressure for the hydraulic functions.
Supplies fluid under pressure to the torque converter, geartrain, electro-hydraulic control unit and the lubrication circuit.
Draws fluid from the fluid pan below the transmission casing, through a filter.

Parking lock
This component prevents movement of the vehicle by engaging a fixed pawl with the parking lock gear located on the output shaft. The pawl is engaged by moving the gear selector lever to the park (P) position.

Electro-hydraulic control unit
This unit, mounted in the transmission lower case, converts signals, mechanical from the J-gate and electrical from the Transmission Control Module (TCM), into hydraulic functions.
The following components are assembled to the unit:
Selector valve.
Shift plate.
Control valve - modulating pressure.
Control valve - shift pressure.
Solenoid valve 1 <-> 2 and 4 <-> 5 shift.
Solenoid valve 3 <-> 4 shift.
Solenoid valve 2 <-> 3 shift.
Solenoid valve - converter lock-up.
Speed sensors (2).
Temperature sensor.

Speed sensors
There are two speed sensors within the transmission assembly which provide input to the TCM. These inputs, when used in conjunction with CAN data relative to engine speed (from Engine Control Module [ECM]) and road speed (from Antilock Brake System [ABS]), are used to electronically control the transmission.

Temperature sensor
The output from this sensor allows the TCM to compensate for the affect of fluid temperature on shift time and quality.