Description & Operation

The 4EAT is a 4-speed transaxle assembly. The 4EAT is controlled by both electronic and mechanical systems. Input signals from sensors are sent to 4EAT control module and computed to determine gear, shift patterns and lock-up timing. The 4EAT control module has built-in self-diagnosis, fail-safe mode and warning code display for the main input sensors and solenoid valves.

Four solenoid valves are located on the valve body. Solenoid valves actuate shifting and torque converter lock-up by switching oil flow through passages within the valve body.

When the lock-up solenoid is switched on, fluid pressure holding the lock-up control valve is drained, allowing valve to open. When valve opens, hydraulic pressure from the rear chamber causes the converter clutch to press tightly against the converter cover. Lock-up occurs and force is transmitted directly to the transaxle with no fluid slippage.

When the 4EAT control module switches lock-up solenoid off, hydraulic pressure in the front chamber becomes greater than pressure in the rear chamber. The converter clutch then moves away from the converter cover and lock-up is released.

The 4EAT transaxle can be operated in manual or automatic shift mode. When the vehicle is started, 4EAT will be in the automatic position. When the manual shift switch is pressed, 4EAT module will activate the manual shift mode. If the manual shift switch is pressed again or ignition is turned off, manual shift will cancel and automatic shift will be resumed.

Shift timing is also affected by the SHIFT MODE switch. When switch is in the NORM position, shift timing provides for maximum fuel efficiency. When switch is in the POWER position, shift timing provides for maximum acceleration.