Part 1

General
The automatic gearbox is a four speed unit with electronic control of gear selection, shift quality and torque converter lock-up. Selections on the selector lever assembly are transmitted to the gearbox by a selector cable. A gear position switch on the gearbox transmits the gear selection to an Electronic Automatic Transmission (EAT) ECU, which outputs the appropriate control signals to an electro-hydraulic valve block in the gearbox. A mode switch enables the driver to change the control mode of the EAT ECU. The EAT ECU operates warning lamps in the instrument pack to indicate the control mode and system status.
The gearbox features a pressure lubrication system and is cooled by pumping the lubricant through an oil cooler.

Selector lever assembly





The selector lever assembly consists of a lever and a cover attached to a base. The base is located on a gasket and secured to the transmission tunnel. The lever is hinged to the base. A latch in the lever engages with detents in the base to provide the lever positions P, R, N, D, 3, 2, 1. The latch is disengaged by pressing a release button on the lever knob. Except for lever movement between positions D and 3, the button must be pressed before the lever can be moved. In some markets, vehicles incorporate an interlock solenoid at the bottom of the lever, which prevents the lever being moved from P unless the ignition switch is in position 11 and the foot brake is applied.
The cover incorporates lever position indicators and the mode switch. The lever position indicators illuminate to show the position of the selector lever. Illumination is controlled by the Body Control Unit (BCU). The mode switch is a non-latching hinged switch that, when pressed, connects an earth to the EAT ECU to request a change of mode.
An electrical connector at the rear of the cover connects the selector lever assembly to the vehicle wiring.

Selector cable
The selector cable is a Bowden type cable that connects the selector lever assembly to a selector lever on the gearbox. 'C' clips secure the ends of the outer cable to brackets on the selector lever assembly and the selector lever.
The inner cable is adjustable at the connection of the inner cable with the gearbox selector lever.

Gearbox





The gearbox consists of a torque converter housing, an intermediate plate, a gearbox housing and a rear extension housing, bolted together in series. The rear of the gearbox is supported by a rubber mounting installed between a mounting bracket on the gearbox and the LH chassis rail. A heat shield is installed on the mounting to protect it from the exhaust.





Sectioned view of gearbox

Torque converter housing
The torque converter housing attaches the gearbox to the engine and contains the torque converter. Different torque converter housings are used to accommodate the difference between the V8 and Td5 engine interfaces. The torque converter is connected to the engine drive plate and transmits the drive from the engine to the gearbox input shaft. When engaged, a hydraulic lock-up clutch in the torque converter prevents slippage, to give a direct drive from the engine to the gearbox for improved driving response.

Intermediate plate
The intermediate plate supports the gearbox input shaft and provides the interface between the transmission fluid pump and the lubrication circuit. The pump attaches to the front of the intermediate plate and is driven by the impeller in the torque converter. The pump pressurizes transmission fluid drawn from the sump on the gearbox housing. The pressurized fluid then circulates through the torque converter and gearbox housing components for cooling, lubrication and gear shift purposes. Ports around the outer periphery of the intermediate plate provide the inlet and outlet connections to the fluid cooler and a pressure take-off point for servicing.

Gearbox housing
The gearbox housing contains two epicyclic gear sets on input and output shafts. Hydraulic brake clutches on the shafts control which elements of the gear sets are engaged, and their direction of rotation, to produce the P and N selections, four forward gear ratios and one reverse gear ratio.





Gear ratios

Valve block





The lock-up and brake clutches are operated by pressurized transmission fluid from the valve block in the sump. A manual valve and four solenoid valves, also known as Motorized Valves (MV), control the supply of pressurized transmission fluid from the valve block:
^ The manual valve controls the supply in P. R. N and D.
^ Solenoid valves MV 1 and MV 2 control the supplies that operate the brake clutches for shift control.
^ Solenoid valve MV 3 controls the supply that operates the lock-up clutch.
^ Solenoid valve MV 4 modulates the pressure of the supplies to the brake clutches, to control shift quality.
Operation of the manual valve is controlled by the selector lever assembly. In the gearbox, a selector shaft engages with the manual valve. The selector shaft is connected to the selector lever assembly via the selector cable and a selector lever on the left side of the gearbox. The selector shaft also operates a mechanism that locks the output shaft when P is selected.

Operation of the solenoid valves is controlled by the EAT ECU.
An output shaft speed sensor in the gearbox housing outputs a signal to the EAT ECU. The EAT ECU compares output shaft speed with engine speed to determine the engaged gear, and output shaft speed with vehicle speed to confirm the range selected on the transfer box.
A bayonet lock electrical connector in the gearbox casing, to the rear of the selector lever, connects the solenoid valves and the output shaft speed sensor to the vehicle wiring.
A pressed steel sump encloses the valve block and collects transmission fluid draining from the gearbox housing. A suction pipe and filter on the underside of the valve block connect to the inlet side of the fluid pump. A magnet is installed in the sump to collect any magnetic particles that may be present. A level plug and a drain plug are installed in the sump for servicing.

Rear extension housing
The rear extension housing provides the interface between the gearbox housing and the transfer box. A splined extension shaft, secured to the gearbox output shaft by a bolt, transmits the drive from the gearbox to the transfer box. A seal in the rear of the housing prevents leakage past the extension shaft. A breather pipe, attached to the left side of the rear extension housing, ventilates the interior of the gearbox and rear extension housings to atmosphere. The open end of the breather pipe is located in the engine compartment at the right rear corner of the engine.

Gearbox power flows
The following Figures show the power flow through the gearbox for each forward gear when D is selected, and for reverse. The key to the Item numbers on the Figures, and in parenthesis in the accompanying text, can be found on the 'Sectioned view of gearbox' Figure, above.





1st Gear (D selected)





2nd Gear (D selected)





3rd Gear (D selected)





4th Gear (D selected)





Reverse gear

Gear position switch
The gear position switch outputs signals that are related to the position of the selector lever assembly. The switch is installed on the selector shaft on the left side of the gearbox. Slotted mounting holes allow the switch to be turned relative to the shaft for adjustment. A fly lead connects the switch to the vehicle wiring.
Movement of the selector lever assembly turns the selector shaft, which operates six pairs of contacts in the switch. The pairs of contacts are identified as the W, X, Y, Z, Park/Neutral and Reverse contacts.
When closed:
^ The W, X, Y and Z contacts output a 12V ignition supply from the BCU.
^ The Park/Neutral contacts output an earth.
^ The Reverse contacts output a 12V ignition supply from the passenger compartment fuse box.
The outputs of the W, X, Y and Z contacts are monitored by the EAT ECU and the BCU to determine the position of the selector lever assembly.





Gear position switch W, X, Y. Z outputs

The Park/Neutral contacts output to the BCU and, on diesel models, the ECM. The Reverse contacts output to the BCU, the reversing lamps, the SLABS ECU and, where fitted, the ACE ECU and the electrochromic interior mirror.

Oil cooler





Transmission fluid from the gearbox is circulated through a cooler attached to the front of the radiator. Quick release connectors on the transmission fluid lines attach to connections on each end tank of the cooler. A temperature sensor on the RH end tank provides the instrument pack with an input of transmission fluid temperature. If the temperature exceeds a preset limit, the instrument pack illuminates the transmission temperature warning lamp. The warning lamp remains illuminated until the temperature of the fluid returns within limits.

EAT ECU

The EAT ECU operates the solenoid valves in the gearbox to provide automatic control of gear shifts and torque converter lock-up. The EAT ECU is attached to a protective bracket which is secured to the cabin floor below the LH front seat. A 55 pin connector links the EAT ECU to the vehicle wiring.
Software in the EAT ECU monitors hard wired inputs and exchanges information with the ECM on a Controller Area Network (CAN) bus to determine gear shift and torque converter lock-up requirements. Resultant control signals are then output to the gearbox solenoid valves.





EAT ECU connector





EAT ECU connector pin details





CAN communications between EAT ECU and ECM

WARNING lamps





WARNING lamps and selector lever position indication

Illumination for each warning lamp is provided by a non serviceable LED.