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 PCM maintains the following adapt parameters for the transmission:
| • | Upshift Adapt - The PCM monitors the Automatic Transmission
Input(Shaft) Speed Sensor (A/T 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 (A/T ISS) and the Vehicle Speed Sensor (VSS) after
a shift and the PCM calculates the amount of slippage in that gear. The PCM
then adjusts the signal to the transmission pressure control solenoid valve
in order to maintain slippage below a set amount. |
| • | Garage Shift Adapt - The PCM monitors the Automatic Transmission
Input(Shaft) Speed Sensor (A/T ISS) during a shift into a given range (P,R,N,D)
and the PCM calculates whether the engagement is occurring too fast or too
slow. The PCM adjusts the PC solenoid valve in order to maintain a set shift
feel. |
| • | WOT 1-2 Adapt - The PCM monitors the Vehicle Speed Sensor
(VSS) and the engine rpm during a 1-2 Wide Open Throttle (WOT) shift. The
PCM will adapt the 1-2 shift point during WOT. |
| • | Learn Tap - Accelerated PLM learn mode. A technician must
road test the vehicle for 15 minutes (normal time 2-3 hrs). |
| | Important: The transmission may experience harsh, soft or mushy shifts for up to
two days later.
|
Transmission adapts must be reset whenever the transmission is overhauled
or replaced. In order to reset transmission adapts, select the following:
- Scan tool
- Miscellaneous test
- A/T outputs
- Clear or reset all adapts
