Chevrolet Silverado / GMC Sierra. Service manual — part 810

STL

Service Transmission Lamp

TAP

Transmission Adaptive Pressure

TCC

Torque Converter Clutch

TFP

Transmission Fluid Pressure

TFT

Transmission Fluid Temperature

TP

Throttle Position

VSS

Vehicle Speed Sensor

WOT

Wide Open Throttle

TRANSMISSION IDENTIFICATION INFORMATION

2008 Chevrolet Silverado 1500

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

Sierra & Silverado

Fig. 199: Transmission Identification Information
Courtesy of GENERAL MOTORS CORP.

Callout

Component Name

1

Model Year

2

Model Code

3

Transmission Family

4

Transmission Assembly Number

2008 Chevrolet Silverado 1500

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

Sierra & Silverado

TRANSMISSION GENERAL DESCRIPTION

The Hydra-matic 6-Speed RWD is a fully automatic, 6-speed, rear-wheel drive, electronic-
controlled transmission. It consists primarily of a 4-element torque converter, an integral fluid
pump and converter housing, a single and double planetary gear set, friction and mechanical
clutch assemblies, and a hydraulic pressurization and control system. There are four variants of
the transmission, all based on torque capacity. Architecture is common between the variants, and
component differences are primarily related to size.

The 4-element torque converter contains a pump, a turbine, a pressure plate splined to the turbine,
and a stator assembly. The torque converter acts as a fluid coupling to smoothly transmit power
from the engine to the transmission. It also hydraulically provides additional torque multiplication
when required. The pressure plate, when applied, provides a mechanical direct drive coupling of
the engine to the transmission.

The planetary gear sets provide the 6 forward gear ratios and reverse. Changing gear ratios is
fully automatic and is accomplished through the use of a transmission control module (TCM)
located inside the transmission. The TCM receives and monitors various electronic sensor inputs
and uses this information to shift the transmission at the optimum time.

The TCM commands shift solenoids and variable bleed pressure control solenoids to control shift
timing and feel. The TCM also controls the apply and release of the torque converter clutch
which allows the engine to deliver the maximum fuel efficiency without sacrificing vehicle
performance. All the solenoids, including the TCM, are packaged into a self-contained control
solenoid valve assembly.

The hydraulic system primarily consists of a vane-type pump, 2 control valve body assemblies,
converter housing and case. The pump maintains the working pressures needed to stroke the
clutch pistons that apply or release the friction components. These friction components, when
applied or released, support the automatic shifting qualities of the transmission.

The friction components used in this transmission consist of 5 multiple disc clutches. The multiple
disc clutches combine with one mechanical sprag clutch to deliver 7 different gear ratios, 6

5

Julian date

6

Sequential Serial Number

7

Source Code

8

Broadcast Code

9

Bar Code

10

Transmission I.D.

2008 Chevrolet Silverado 1500

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

Sierra & Silverado

forward and one reverse, through the gear sets. The gear sets then transfer torque through the
output shaft.

The transmission may be operated in any of the following gear ranges:

PARK (P)

This position locks the rear wheels and prevents the vehicle from rolling either forward or
backward. PARK is the best position to use when starting the vehicle. Because the
transmission utilizes a shift lock control system, it is necessary to fully depress the brake
pedal before shifting out of PARK. For safety reasons, use the parking brake in addition to
the PARK position.

REVERSE (R)

This position allows the vehicle to be operated in a rearward direction.

NEUTRAL (N)

This position allows the engine to be started and operated while driving the vehicle. If
necessary, you may select this position in order to restart the engine with the vehicle
moving. This position should also be used when towing the vehicle.

DRIVE (D)

Drive range should be used for all normal driving conditions for maximum efficiency and
fuel economy. Drive range allows the transmission to operate in each of the 6 forward gear
ratios. Downshifts to a lower gear, or higher gear ratio, are available for safe passing by
depressing the accelerator or by manually selecting a lower gear in the manual mode range.

MANUAL MODE (M)

This position allows the driver to select a range of gears appropriate for current driving
conditions. Refer to the vehicle owner's manual for specific manual mode information.

TRANSMISSION COMPONENT AND SYSTEM DESCRIPTION

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

A torque converter with an electronically controlled capacity clutch (ECCC). ECCC was
developed to reduce the possibility of noise, vibration, or chuggle caused by TCC apply. In

2008 Chevrolet Silverado 1500

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

Sierra & Silverado