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Automatic Transmission/Transaxle: Description and Operation
DESCRIPTIONCross-Sectional View Of A4LD Transmission:
The transmission is fully automatic with four forward and one reverse speed.
CONSTRUCTION
The transmission consist of a welded lockup torque converter assembly and a three unit planetary gear train. Electronic controls for the transmission are integrated into the on-board EEC-IV or EEC-V systems. Sensors provide inputs to the Powertrain Control Module (PCM).
OPERATION
A speed and load sensitive, pressure controlled hydraulic system is used for gear selection and automatic shift control. Torque converter operation is controlled by the PCM. These controls, along with hydraulic controls in the valve body, operate a piston plate clutch in the torque converter that eliminates torque converter slip when applied. The pressure controlled valve body, besides supplying fluid for torque converter operation, piston plate clutch application, and pressure for applying bands, also contains an on-board computer controlled solenoid which electrically overrides the application of the piston plate clutch in the converter.