General Description

4F3OE Cutaway (Part 1 of 2):

Part 2 Of 2:

The 4F20E electronically controlled automatic transaxle features a combination of electronic and mechanical systems to control forward gear shifting, torque converter lockup for quietness and economy, and a self-diagnosis capability for simplifying troubleshooting procedures.

The electronic system controls the transaxle shifting in forward speeds and controls torque converter lockup by means of solenoid actuated shift valves. Electronically controlled solenoids control hydraulic circuits to the shift valves. These shift valves, when hydraulically actuated, actuate friction elements (clutches and band) to control operation of the planetary gearset. The shift timing and lockup events are regulated by the Transmission Control Module (TCM) in programmed logic and in response to input sensors and switches to produce optimum driveability. The TCM and the Powertrain Control Module (PCM) are both used to determine other operational characteristics, such as reducing torque or retard ignition timing for smooth and responsive shift performance.

The overdrive (O/D) control switch is used to inhibit fourth gear operation. The O/D OFF lamp on the instrument panel will illuminate when fourth gear has been "locked out." If the O/D control switch is depressed during fourth gear operation, a 4-3 downshift will occur. The O/D control switch should be used when descending hills or during city driving to increase engine braking. The O/D control switch is located on the end of the shift control selector lever.