Component Description
Introduction
Component Descriptions
The torque converter:
- Acts as a fluid coupling between the engine and transmission geartrain.
- Provides multiplication of engine torque.
- Consists of an impeller, turbine and stator, housed within a converter cover.
- Has a lock-up clutch with variable slip control.
The transmission casing:
- Houses the geartrain and electro-hydraulic control unit.
- Contains the input speed sensor which measures turbine speed.
- Contains the output speed sensor which measures the transmission output speed.
- Contains the hydraulic system pump.
- Contains the fluid temperature sensor.
The epicyclic geartrain:
- Provides five forward gears and Reverse.
- Has hydraulically actuated, multi-disk clutches, to select the required gear ratios.
- Features clutch-to-clutch operation to permit gear shifts for uninterrupted power flow.
The electro-hydraulic control unit:
- Is located in the lower part of the unit, within the fluid pan.
- Is controlled by the TCM (transmission control module), and the manual selector valve which is cable operated.
- Regulates the flow of fluid to the geartrain clutches via three solenoid-operated valves and the manual selector valve.
- Has five pressure regulators for controlling fluid pressures within the system.
- Is connected to the TCM via a 16-way connector mounted on the left-hand side of the transmission casing. Refer to Connector Pins identification.
The hydraulic system pump:
- Is located at the front of the transmission casing.
- Is driven from the impeller hub, pressurizing the fluid whenever the engine is running.
- 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.
The rear extension housing:
- Is bolted to the rear of the transmission casing.
- Provides the rear engine/transmission mounting point.
- Carries the transmission output shaft oil seal.
Filled-for-life Fluid System
The transmission is 'filled for life' and does not require fluid changes, except where extreme driving conditions prevail. Routine level checking is not required and a dipstick is not provided. A level/filler plug is fitted for level checking and replenishment, following service actions.
Hydraulic Control - Transmission Pressure Regulators and Shift Solenoids
Operation
Fluid flow within the transmission assembly is controlled by three solenoid valves and five pressure regulators.
The TCM supplies an internally switched +12V supply to each shift solenoid and pressure regulator. Hydraulic pressure from the pressure regulators is controlled by 'pulse width modulation' (PWM) of the ground switching signal i.e. the duty cycle, the time that the pressure regulator is switched on. Control of the solenoids is effected by switching one side to ground through the TCM.
During normal operation the TCM monitors 'Switch On' of the solenoids, regulators and the TCM output stages, but does not check output stage 'Switch Off'.
Voltage is monitored at the regulators and solenoids for continuity and shorts. For example, when a solenoid is ON the voltage on the TCM side should be ground, when OFF the voltage should be +12.
Shift Solenoid
The function of the three solenoid valves is to control the flow of transmission oil to the various transmission components. Three solenoid valves are located within the transmission assembly, and are closed when not energized.
Pressure Regulator
The function of the five pressure regulators is to modulate the oil pressure to the various transmission components. The regulators are pulse width modulated by the TCM, switching to ground potential. The other side of the regulators being connected, via an internal TCM relay, to battery voltage. The regulator is closed when not energized by the TCM.