Transmission System

Transmission System

Introduction

Control Systems

Hydraulic control
The selector valve is operated directly by the J-gate and directs fluid flow for P R N D. Of the four solenoid valves, 3 control shifts and 1 controls converter lock-up. One control valve controls modulating pressure and the other shift pressure.
Regulating valves are used to maintain/control pressure for lubrication, normal operating functions, and the supply to the control valves and shift valves.
In the event of a system fault, the TCM will adopt 'limp home' mode.

Electrical control - TCM
The Transmission Control Module (TCM) controls the transmission internal components thus determining gear selection and shift pattern.





Location
The TCM is located in the same housing as the ECM and is accessed in the same manner. With the two connectors unplugged the TCM may be withdrawn, complete with mounting bracket. System Functions





'J' Gate Layout

Range Selection
The 'J' gate selector lever is connected to the transmission via a cable which operates the transmission selector shaft between positions P R N D only. The shift lever disconnects from the cable when the lever is moved across the gate from D to 4.
Movement of the lever between P R N D manually controls the flow of transmission fluid, the TCM having control of the forward gear selected in D.
Movement of the lever to 4, 3 and 2 positions does not manually modify the fluid flow, the TCM detects these positions using the DILS and controls the ratios electronically by energizing solenoids.

Shift Point Control
The gearshift points are controlled, by the TCM, as a function of the output speed, engine load, selector position and shift program selected. The operator has control over the shift points via the shift lever, throttle pedal movement, kickdown function and mode switch.

Mode Switch
This switch allows operator selection of two base shift modes; Normal and Sport; the switch being illuminated when Sport is selected. This function alters the values in the TCM shift point calculations.

Shift Programs
Upon encountering the following conditions, the TCM will automatically use the Normal or Sports shift map to enhance the operation of the vehicle:
1. Traction: When traction intervention is active.
2. Hot mode: Extreme engine/transmission temperatures.
3. Gradient: Under specific speeds and loads.
4. Manual: Driver initiated override of the normal shift map when the LH side of the 'J gate' is used.

Traction
When traction or stability control (engine or brake system derived) is operational the TCM will implement the traction map to maximize control of wheel slip.

Gradient
The gradient function is intended to enhance vehicle driveability when climbing a gradient or towing. The TCM will implement the function when increased driving resistance is detected, and provides enhanced driveability, additional cooling and/or increased performance as appropriate.

Serial Communications Interfaces

Controller Area Network (CAN)
The TCM is an integral part of the CAN system which facilitates the interchange of real-time data between control modules and sensors.