Transmission Adaptive Functions

Transmission Adaptive Functions
The 4T40 automatic transmission uses a line pressure control system, which has the ability to continuously adapt the system line pressure. This compensates for normal wear of the following parts:
^ The clutch fiber plates
^ The seals
^ The springs

The powertrain control module (PCM)/transmission control module (TCM) maintains the Upshift Adapt parameters for the transmission. The PCM/TCM monitors the input speed sensor (ISS) and the output speed sensor (OSS) during commanded shifts in order to determine if a shift is occurring too fast or too slow. The PCM/TCM adjusts the signal from the transmission pressure control (PC) solenoid in order to maintain a set shift feel.

Transmission adapts must be set again when the transmission is overhauled or replaced. In order to set the transmission adapts again, select the following:
1. Scan Tool
2. Transmission/Transaxle
3. Special Functions
4. Reset Transmission Adapts