Chevrolet Silverado / GMC Sierra. 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