Chevrolet Silverado / GMC Sierra. Service manual — part 839

HIGH STALL SPEEDS (STALL IN RANGES 1-6)

LOW STALL SPEEDS (STALL IN RANGES 1-6)

Low main pressure

Refer to Low Main Line Pressure in All
Ranges and Low Main Line Pressure in
Specific Ranges, Normal Pressure in Other
Ranges.

Leaking pressure control solenoids

Repair or replace the pressure control
solenoids. Refer to Control Valve Solenoid
Replacement (SS1, SS2, SS3, TCC, and
MAIN MOD) or Control Valve Solenoid
Replacement (PCS1 and PCS2).

Erratic speed sensor signal

Refer to the speed sensor DTCs.

Piston seals leaking or clutch plates slipping
in range involved

Overhaul the transmission.

Condition

Action

Not in gear

Select D, DRIVE.

Low fluid level, aerated fluid

Add fluid to the proper level. Refer to
Transmission Fluid Check.

Faulty torque converter

Replace the torque converter. Refer to
Torque Converter Replacement.

Incorrect torque converter

Replace the torque converter. Refer to
Torque Converter Replacement.

Clutch pressure low

Refer to Low Main Line Pressure in
Specific Ranges, Normal Pressure in Other
Ranges.

1-2-3-4 clutch or Low and Reverse clutch or
2-6 clutch slipping
Use the diagnostic tool to measure turbine
speed.

Rebuild the 1-2-3-4 clutch or the Low and
Reverse clutch or the 2-6 clutch.

Higher power engine

Confirm proper engine match.

Condition

Action

Engine not performing efficiently

Plugged or restricted injectors

Refer to appropriate engine article.
The following specific sections should be
helpful in defining the condition:

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

TRANSMISSION WILL NOT MAKE A SPECIFIC SHIFT

TRANSMISSION WILL NOT STAY IN FORWARD OR REVERSE

High altitude conditions

Dirty air filters

Incorrect fuel/valve timing

Throttle linkage broken or not adjusted
correctly

Electronic engine controls condition

Refer to Diagnostic System Check -
Vehicle .

Refer to Symptoms - Engine
Mechanical .

Stall speeds of 33% of normal implies
freewheeling stator

Replace the converter assembly. Refer to
Torque Converter Replacement.

Engine smoke controls

Compare lugback vs. static stall speed.

Incorrect torque converter

Install the correct torque converter. Refer to
Torque Converter Replacement.

Condition

Action

Low engine power

Correct the engine condition.

Extreme fluid temperature

Inspect the cooling system and fluid level.
Refer to Transmission Fluid Check.

Faulty speed sensor/circuit

Repair the circuit or replace the speed sensor
or sensors. Refer to Speed Sensor
Replacement.

Faulty temperature sensor/circuit

Inspect for a temperature reading which
inhibits shifts.

Faulty or misadjusted shift selector

Repair the shift selector.

Condition

Action

Low fluid

Adjust the fluid level. Refer to Transmission
Fluid Check.

Leaking at solenoid assembly

Replace the solenoid assembly. Refer to
Control Valve Solenoid Replacement (SS1,
SS2, SS3, TCC, and MAIN MOD) or

Control Valve Solenoid Replacement
(PCS1 and PCS2)

.

Low pressure

Repair the transmission.

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

TRANSMISSION WILL NOT SHIFT TO FORWARD OR REVERSE

TRANSMISSION OVERHEATS

Faulty solenoid - leaking

Replace the solenoid. Refer to Control Valve
Solenoid Replacement (SS1, SS2, SS3,
TCC, and MAIN MOD) or Control Valve
Solenoid Replacement (PCS1 and PCS2).

Condition

Action

Engine RPM too high

Reduce the engine RPM. It may be necessary
to select NEUTRAL, and then D or R again.

Low fluid level

Add fluid to the proper level. Refer to
Transmission Fluid Check.

Faulty throttle signal from engine

Correct the engine throttle signal.

Shift selector is not functioning properly

Repair the shift selector.

Speed sensor or sensors not functioning
properly

Repair or replace the speed sensor or sensors
or circuitry. Refer to Speed Sensor
Replacement.

Mechanical failure to Low and Reverse
clutch

Repair the transmission.

Mechanical failure in transmission torque
converter, shafts, or planetaries

Repair the transmission.

Low pressure

Repair the transmission.

Faulty wiring in transmission control
module (TCM) input/output function
circuits

Correct the circuit wiring.

Condition

Action

Aerated fluid - incorrect fluid level

Adjust fluid to the proper level. Refer to
Transmission Fluid Check.

Inspect for a defective pump.

Air flow to cooler obstructed

Remove the air flow obstruction.

Engine overheat

Correct the overheating condition. Refer to
Symptoms - Engine Cooling in Engine
Cooling.

Inaccurate temperature gauge or sending

Replace the gauge and/or sending unit.

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado

TRANSMISSION DOES NOT SHIFT PROPERLY

unit
Inaccurate sump temperature sensor

Replace the pressure switch manifold (PSM)
or internal harness. Refer to Pressure Switch
Manifold Replacement or

Wiring Harness

Replacement

.

Excessive cooler circuit pressure drop

Inspect for plugged cooler, lines too small,
collapsed hose, too many elbows in circuit.

Transmission cooler lines reversed

Connect the cooler lines properly. Oil and
water should flow in opposite directions.

Fluid cooler lines restricted

Remove restrictions and clean or replace the
lines. Refer to Transmission Fluid Cooler
Hose/Pipe Replacement.

Torque converter - wrong converter, no
torque converter clutch, stuck stator, or
slipping stator

Replace or repair the converter assembly.
Refer to Torque Converter Replacement.
A stuck stator will not allow cool down in
Neutral.

Cooler flow loss due to internal transmission
leakage

Overhaul the transmission.

Condition

Action

Engine idle speed too fast during
NEUTRAL to range shift

Adjust to correct idle speed.

Faulty throttle sensor/circuit

Repair or replace the sensor or circuit.

Faulty or sticking bleed ball in 1-2-3-4
clutch piston housing

Repair the transmission.

Excessive clutch running clearance

Rebuild the transmission and adjust clearances.

Shift adaptives not converged

Refer to FastLearn Procedure.

Instrument panel tachometer incorrect

Repair or replace the tachometer.

Incorrectly calibrated electronic
speedometer

Calibrate the electronic speedometer.

Faulty speed sensor/circuit

Repair the circuit or replace the speed sensor.
Refer to the speed sensor DTCs.

Loose speed sensor

Tighten the speed sensor retaining bracket
bolt. Refer to Speed Sensor Replacement.

Degraded fluid

Change the transmission fluid and filter. Refer

2008 Chevrolet Silverado 1500

2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &

Silverado