Overhaul - La4A-El: Description

The LA4A-EL is a 4-speed automatic transmission that is controlled by both electronic and mechanical systems utilizing a compound planetary gearset, chain drive, final drive planetary gearset and an open differential. One band, 5 friction clutches, and 2 one-way clutches provide 4 forward gear ratios and reverse.

Input signals from sensors are sent to the Powertrain Control Module (PCM). The PCM can determine when the time and conditions are right for a shift or converter clutch application. The PCM can also determine line pressure needed to optimize shift feel. The 5 electronic solenoids accomplish the following functions:

• Two On/Off solenoids for shifting.
• One Pulse-Width Modulator (PWM) solenoid for Torque Converter Clutch (TCC) control.
• One Electronic Pressure Control (EPC) solenoid for line pressure control.
• One 3-2 timing/coast clutch solenoid to control release of coast clutch, coordinated release of the direct clutch, and apply of the low and intermediate band.

PCM has built-in self-diagnosis, fail-safe code and warning code display for the main input sensors and solenoid valves.