DESCRIPTION
The 4L80-E transmission uses 2 electric shift solenoids to control transmission upshifts and downshifts. In addition, a pressure control (force motor) solenoid controls hydraulic line pressure, and a Torque Converter Clutch (TCC) Pulse Width Modulated (PWM) solenoid is used to control fluid acting on converter clutch valve, which then controls TCC apply and release. Solenoids are turned on and off by a Powertrain Control Module (PCM) or a Transmission Control Module (TCM).
PCM/TCM receives signals from various transmission sensors. Sensors include engine speed and throttle position, transmission speed, hydraulic pressure and transmission fluid temperature. PCM/TCM has on-board self-diagnostics to help identify any parts or circuits which may need further testing.
OPERATION
Shift solenoid holds hydraulic pressure (solenoid on) or releases hydraulic pressure (solenoid off). This action controls shift valves inside valve body. By switching one or both solenoids on or off, different combinations of clutches, sprags and bands are operated. See CLUTCH AND BAND APPLICATION under TROUBLE SHOOTING.