Chevrolet Silverado / GMC Sierra. Manual - part 840
ABNORMAL ACTIVITIES OR RESPONSES
ON-VEHICLE REPAIR INFORMATION
TRANSMISSION CONTROL MODULE REPLACEMENT
to Automatic Transmission Fluid and
Filter Replacement.
Incorrect fluid level
Correct the fluid level. Refer to Transmission
Fluid Check.
Low main pressure
Repair the transmission.
Intermittent conditions
Inspect the wiring harnesses and connectors.
Loose or damaged speed gear
Tighten the output flange bolt or replace the
speed gear.
Sticking valves in the control valve body
Overhaul the control valve body assembly.
Leaking pressure control solenoids
Repair or replace the pressure control
solenoids.
Condition
Action
Excessive Creep in First and Reverse Gears
Engine idle speed too high
Adjust to the correct idle speed.
Vehicle Moves Forward in Neutral
1-2-3-4 clutch failed or not released
Rebuild the 1-2-3-4 clutch.
Vehicle Moves Backward in Neutral
3rd, 5th and reverse clutch failed or not
released
Rebuild the 3rd, 5th and reverse clutch
assembly.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Fig. 8: Transmission Control Module Replacement
Courtesy of GENERAL MOTORS CORP.
Callout
Component Name
Transmission Control Module (TCM)
Procedure
1. Disconnect the TCM electrical connector.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
CONTROL VALVE SOLENOID REPLACEMENT (SS1, SS2, SS3, TCC, AND MAIN MOD)
Removal Procedure
Fig. 9: Locating Shift Solenoid
Courtesy of GENERAL MOTORS CORP.
1. Remove the oil pan and the transmission internal oil filter. Refer to Oil Pan Replacement.
2. Disconnect the internal wiring harness from the solenoid being changed.
3. Remove the solenoid retainer (2) for shift solenoid 1 (SS1) (5). Note the position of the
solenoid connector and pull the solenoid (5) out of the bore in the control valve assembly
(1). The O-rings (3 and 4) provide the resistance felt during removal.
1
2. A new TCM requires programming. Refer to Control Module
References .
Tip: Twisting or tilting of the transmission control module electrical connector
while disconnecting may result in bent or misaligned electrical terminal pins.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
Fig. 10: Identifying Control Valve Solenoids
Courtesy of GENERAL MOTORS CORP.
4. Remove the solenoid retainer (6) for shift solenoid 2 (SS2) (1) or shift solenoid 3 (SS3) (4),
whichever is being replaced.
5. Note the position of the solenoid connector and pull the solenoid out of the bore in the
control valve assembly. The O-rings (2 and 3) provide the resistance felt during removal.
6. Remove the TCC PCS retaining bolt and retaining bracket.
7. Remove the TCC PCS (7).
IMPORTANT: The TCC pressure control solenoid (PCS) retaining bracket
must not be modified. Note that the angle between the 2
bracket surfaces is less than 90 degrees. Replace the
bracket if the angle is 90 degrees or greater.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado