For 1990-2009 cars only
The 4T80-E transmission uses a line pressure control system, which has the ability to continuously adapt the system's line pressure. This compensates for normal wear of the following parts:
| • | The clutch fiber plates |
| • | The seals |
| • | The springs |
The PCM maintains the following adapt parameters for the transmission:
| • | Upshift Adapt - The PCM monitors the automatic transmission input, shaft, speed sensor (AT ISS) and the vehicle speed sensor (VSS) during commanded shifts in order to determine if a shift is occurring too fast or too slow. The PCM adjusts the signal to the transmission pressure control solenoid valve in order to maintain a set shift feel. |
| • | Steady State Adapt - The PCM monitors the automatic transmission input, shaft, speed sensor (AT ISS) and the vehicle speed sensor (VSS) after a shift and the PCM calculates the amount of shift time in that gear. The PCM then adjusts the signal to the transmission pressure control solenoid valve in order to maintain shift time below a set amount. |
Important: The transmission may experience harsh, soft or mushy shifts for up to two days after the adapts are cleared.
Transmission adapts must be cleared whenever the transmission is overhauled or replaced. In order to clear transmission adapts, select the following:
- Scan tool
- Special Functions
- Transmission Output Controls
- Clear TAP
