Chevrolet Silverado / GMC Sierra. Service manual — part 811

a torque converter with ECCC, the pressure plate does not always fully lock to the torque
converter cover. Instead, the pressure plate maintains a small amount of slippage. In RWD
6-Speed transmissions, this slippage can range from 0-50 RPM. Full lockup (0 RPM slip) is
still available on some applications. TCC may apply in 2nd, 3rd, 4th, 5th, or 6th gears. The
specific TCC apply points and the amount of clutch slippage are determined by a number of
operating conditions, including throttle position, vehicle speed, gear, as well as specific
vehicle application. Transmission fluid temperature will also affect TCC apply points.

Vane-type fluid pump assembly

1-2-3-4 and 3-5 Reverse clutch assembly

Input sun gear and carrier assembly

4-5-6 clutch assembly with turbine shaft

4-5-6 clutch hub assembly

1-2-3-4 clutch hub assembly

2-6 and 3-5 reverse clutch hub assembly

Center support assembly, with 2-6 clutch assembly, and low and Reverse clutch assembly

Low clutch sprag assembly

A double planetary output carrier assembly

Output shaft assembly

Control valve body assembly

The electrical components of the 6-Speed RWD are as follows:

Input and output speed sensor assembly

Manual shift shaft position switch

Control solenoid valve assembly, which contains the following components:

Transmission control module (TCM)

5 variable bleed line pressure control (PC) solenoids

Transmission fluid pressure (TFP) switch assembly

Torque converter clutch (TCC) pressure control solenoid

2 shift solenoids

For more information, refer to Electronic Component Description.

TRANSMISSION ADAPTIVE FUNCTIONS

The 6L80 transmission utilizes a line pressure control system during upshifts to compensate for

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - 6L50/6L80/6L90 - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

the normal wear of transmission components. As the apply components within the transmission
wear or change over time, shift time (the time required to apply a clutch) increase or decreases. In
order to compensate for these changes, the transmission control module (TCM) adjusts the
pressure commands to the various PC solenoids, to maintain the originally calibrated shift timing.
The automatic adjusting process is referred to as "adaptive learning" and it is used to ensure
consistent shift feel plus increase transmission durability. The TCM monitors the A/T input speed
sensor (ISS) and the A/T output speed sensor (OSS) during commanded shifts to determine if a
shift is occurring too fast (harsh) or too slow (soft) and adjusts the corresponding pressure control
(PC) solenoid signal to maintain the set shift feel.

The purpose of the adapt function is to automatically compensate the shift quality for the various
vehicle shift control systems. The adapt function is a continuous process that will help to maintain
optimal shift quality throughout the life of the vehicle.

TRANSMISSION INDICATORS AND MESSAGES

The following transmission-related indicators and messages may be displayed on the Instrument
Panel Cluster (IPC). For a complete listing and description of all vehicle indicators and messages,
refer to Indicator/Warning Message Description and Operation .

"TRANSMISSION HOT IDLE ENGINE"

This message is displayed when the TCM detects a transmission fluid temperature (TFT)
equal to or greater than 130°C (266°F) for 5 seconds.

"SERVICE TRANSMISSION"

This message displays when there is a problem with the transmission.

ELECTRONIC COMPONENT DESCRIPTION

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - 6L50/6L80/6L90 - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Fig. 200: Control Solenoid (W/Body and TCM) Valve Assembly
Courtesy of GENERAL MOTORS CORP.

The control solenoid (w/body and TCM) valve assembly contains the following components:

Callout

Component Name

1

Line Pressure Control (PC) Solenoid

2

Torque Converter Clutch (TCC) Pressure Control (PC) Solenoid

3

Shift Solenoid (SS) 2

4

16 Pin Connector

5

Pressure Control (PC) Solenoid 3

6

Transmission Fluid Pressure (TFP) Switch 5

7

Pressure Control (PC) Solenoid 4

8

Pressure Control (PC) Solenoid 2

9

Transmission Fluid Pressure (TFP) Switch 3

10

Transmission Fluid Pressure (TFP) Switch 1

11

Transmission Fluid Pressure (TFP) Switch 4

12

Pressure Control (PC) Solenoid 5

13

Shift Solenoid (SS) 1

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - 6L50/6L80/6L90 - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado

Transmission control module (TCM)

Clutch pressure control solenoids (Clutch PC Sol)

Shift solenoids (SS)

Line pressure control solenoid (Line PC Sol)

Torque converter clutch pressure control solenoid (TCC PC Sol)

Transmission fluid temperature sensor (TFT Sensor)

TCM temperature sensor

Power-up temperature sensor

Transmission fluid pressure switches (TFP Sw)

These components are not serviced separately. The control solenoid (w/body and TCM) valve
assembly utilizes a lead-frame system to connect these components electrically to the TCM. No
wires are used for these components. The control solenoid (w/body and TCM) valve assembly
bolts directly to the lower and upper valve body assemblies inside the transmission. The control
solenoid (w/body and TCM) valve assembly connects to the engine harness 16-way connector via
a pass-thru sleeve.

INTERNAL MODE SWITCH (IMS)

Fig. 201: Identifying Internal Mode Switch (IMS)
Courtesy of GENERAL MOTORS CORP.

The transmission manual shift shaft switch assembly is a sliding contact switch attached to the
manual shift shaft inside the transmission case. The five inputs to the TCM from the transmission
manual shift shaft switch assembly indicate the transmission gear selector lever position. This

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - 6L50/6L80/6L90 - Cab & Chassis Sierra, Cab & Chassis Silverado,

Sierra & Silverado