Transmission Component and System Description

The mechanical components of this unit are as follows:
- A torque converter with a torque converter clutch (TCC)
- A drive link assembly
- 4th and Lo/Reverse band assemblies
- Forward, coast, 2nd and 3rd multiple disc clutches
- Two planetary gear sets
- Two sprag clutches (Forward and 2nd)
- One roller clutch (Lo)
- Three fluid pumps
- Two control valve assemblies
- A final drive assembly with a bolted on case extension
The electrical components of this unit are as follows:
- Two shift solenoid valves, 1-2 and 2-3
- A torque converter clutch solenoid valve
- A transmission pressure control (PC) solenoid valve
- An automatic transmission fluid temperature (TFT) sensor
- Two speed sensors: input and vehicle speed sensor
- An automatic transmission fluid pressure (TFP) manual valve position switch
- An automatic transmission wiring harness
- An internal mode switch
- A wire harness extension
Refer to Electronic Component Description.

Dry Sump Oil System
This transmission uses a dry sump method of operation. There is no reservoir of fluid in the bottom pan during operation. The majority of fluid remains in the side pan. Fluid is continuously supplied from the bottom pan to the upper valve body. The upper valve body distributes fluid to the necessary components. The three pumps operate in the following manner:
- Scavenger Pump - This pump continuously supplies fluid to the side pan by scavenging oil from the bottom pan.
- Primary Pump - This pump operates on fluid from the scavenger pump and supplies line pressure for all gear ranges.
- Secondary Pump - During demand driving situations such as forced throttle downshifts, wide open throttle upshifts, and Reverse, this pump helps the primary pump to reach the boosted line pressures that are needed. The secondary pump also helps supply the fluid capacity to the necessary clutches during initial engagement.

Adapt Function
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 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 (AT 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 PCM learn mode. A technician must road test the vehicle for 15 minutes (normal time 2-3 hours).

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:
1. Scan tool
2. Special Functions
3. Transmission Output Controls
4. Reset Adapts