Automatic Transmission/Transaxle: Description and Operation
DESCRIPTIONSectional View of Ford 4EAT Automatic Transaxle:
The electronically controlled automatic transaxle system features a combination of electronic and mechanical systems to control forward gear shifting and torque converter lock-up for quietness and economy, and self-diagnosis capability for simplifying diagnostic procedures. Capri and Probe models are equipped with a manual switch for slow driving on steep or slippery surfaces.
CONSTRUCTION
A unique mechanical feature of the 4EAT automatic transaxle is the single compact combination type 4-speed planetary gear instead of the usual two planetary gears used in 3-speed transaxles. This allows for an overall size reduction. Another unique feature is the variable capacity oil pump. This pump provides a constant oil quantity at and above medium speed to reduce power losses caused by pumping more oil than necessary at higher speeds.
OPERATION
The electronic system controls transaxle shifting in forward speeds and controls torque converter lock-up through solenoid operated valves. When energized (ON), the solenoid valves actuate clutches and bands to control planetary gear shifting. Shift timing and torque converter lock-up are regulated by the control unit with programmed logic and in response to input sensors and switches to produce optimum driveability.