Automatic gearbox - ZF4HP22/24 (Oil cooler): Description and operation

Oil cooler

1 Inlet connection 2 Fixing bracket 3 Outlet connection 4 Fixing bracket 5 Temperature sensor

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.