Chevrolet Silverado / GMC Sierra. Manual - part 838
FLUID LEAKS FROM FLUID FILL TUBE AND/OR VENT
FLUID LEAKS FROM TRANSMISSION INPUT
Low and Reverse clutch slipping, leaks at
piston seals, Low and Reverse clutch plates
worn
Inspect the Low and Reverse clutch plates and
piston seals. Replace/rebuild as necessary.
Condition
Action
Dipstick loose
Tighten the cap. Replace the cap if necessary.
Fluid level too high
Drain the fluid to the proper level. Refer to
Transmission Fluid Check.
Fluid level too low
Add fluid to the proper level. Refer to
Transmission Fluid Check.
Breather stopped up - clogged
Clean or replace the breather.
Dipstick or fill tube seal worn
Replace the seals or dipstick.
Incorrect dipstick marking
Calibrate the dipstick.
Fluid contaminated with engine coolant or
water
Drain and replace fluid. Locate and fix source
of additional fluid. Refer to Transmission
Fluid Check andAutomatic Transmission
Fluid and Filter Replacement.
Condition
Action
Torque converter seal leaks
Replace the torque converter seal. Refer to
Torque Converter Fluid Seal Replacement.
Front support bolt seals leaking
Replace the bolt seals. Refer to Torque
Converter Housing Bolt Seal Replacement.
Converter leaks
Inspect the converter seals, cracked converter
pump tangs, converter cover, or converter
housing porosity. Replace the parts as
required.
Spin-on filter leaking
Replace the filter. Refer to Automatic
Transmission Fluid and Filter
Replacement.
Main pressure plug leak
Replace or torque the main pressure plug.
Refer to Automatic Transmission Fluid
Pressure Test Hole Plug Replacement.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
FLUID LEAKS FROM TRANSMISSION OUTPUT
INTERMITTENT BUZZING NOISE
Pump bushing shows excessive wear
Rebuild and repair the pump.
Condition
Action
Faulty or missing seal at output flange/yoke Install a new seal assembly in the transmission
rear cover. Refer to Rear Propshaft Shaft
Seal Replacement.
Machine lead on output flange/yoke seal
surface
Replace the flange/yoke. Refer to Output
Flange/Yoke Replacement.
Rear cover porosity
Repair or replace the cover.
Flange/yoke worn at seal surface
Replace the flange/yoke. Refer to Output
Flange/Yoke Replacement.
Insufficient sealant around seal OD
Install a new seal assembly in the transmission
rear cover. Refer to Rear Propshaft Shaft
Seal Replacement.
Damaged or missing output bolt washer seal Replace the output bolt sealing washer. Refer
to Output Flange/Yoke Replacement.
Damaged, missing, or loose output flange
bolt
Replace and/or torque the output flange bolt.
Refer to Output Flange/Yoke Replacement.
Condition
Action
Low fluid level
Add fluid to the proper level. Refer to
Transmission Fluid Check.
Air leak in oil suction filter canister
Replace the oil suction filter. Refer to Oil Pan
Replacement.
Clogged suction filter
Replace the filter. Refer to Oil Pan
Replacement.
Aerated fluid causes noisy pump
Correct the fluid level. Refer to Transmission
Fluid Check.
Low main pressure causes main regulator
valve to oscillate
Refer to Low Main Line Pressure in All
Ranges and Low Main Line Pressure in
Specific Ranges, Normal Pressure in Other
Ranges.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
LOW MAIN LINE PRESSURE IN ALL RANGES
LOW MAIN LINE PRESSURE IN SPECIFIC RANGES, NORMAL PRESSURE
IN OTHER RANGES
LOW LUBRICATION PRESSURE
Condition
Action
Incorrect fluid level
Correct the fluid level. Refer to
Transmission Fluid Check.
Plugged or faulty suction filter
Clean or replace the oil suction filter element.
Refer to Oil Pan Replacement.
Main pressure regulator valve sticking
Overhaul the control module assembly.
Leaking solenoids in control valve body
assembly
Replace the solenoids. Refer to Control
Valve Solenoid Replacement (SS1, SS2,
SS3, TCC, and MAIN MOD) or Control
Valve Solenoid Replacement (PCS1 and
PCS2).
Main pressure regulator valve spring weak,
broken, or missing
Inspect the spring and replace, if necessary.
Control module body leakage - separator
plate not flat, loose control valve body bolts
Replace or rebuild the control module
assembly. Care should be taken when
removing and labeling shift springs.
Faulty or incorrect fluid pressure gage
Repair or replace the gage.
Oil pump worn or damaged
Replace or rebuild the oil pump.
Leak in suction circuit
Inspect the suction circuit for leaking seal,
gasket, or mating surface.
Condition
Action
Seal leak
Replace the seals that are causing low
pressure in a particular range.
Condition
Action
Incorrect fluid level
Correct the fluid level. Refer to
Transmission Fluid Check.
Plugged suction filter
Clean or replace the oil suction filter. Refer to
Oil Pan Replacement.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado
CONTAMINATED TRANSMISSION FLUID
EXCESSIVE FLARE - ENGINE OVERSPEED ON WIDE-OPEN THROTTLE
Plugged control main filter
Replace the filter.
Excessive internal fluid leakage
Inspect other pressures. Refer to Low
Main Line Pressure in All Ranges and
Low Main Line Pressure in Specific
Ranges, Normal Pressure in Other
Ranges.
Inspect the control module mounting
bolts.
Inspect the lubrication valve and spring.
Inspect the converter housing to
separator plate gasket.
Cooler lines restricted or leaking
Inspect for kinks and leakage. Reroute or
replace lines as necessary.
Lubrication regulator valve sticking
Clean or replace the regulator valve.
Converter relief valve sticking
Clean or replace the converter relief valve.
Cooler plugged
Clean or replace the cooler.
Faulty gage
Repair or replace the gage.
Condition
Action
Failure to change fluid and filters
Change the fluid and install new filters. Refer
to Automatic Transmission Fluid and
Filter Replacement.
Excessive heat
Inspect the cooling system for restrictions and
proper capacity.
Substandard fluid
Use recommended fluid. Refer to
Transmission General Specifications .
Clutch/transmission failure
Overhaul the transmission.
Condition
Action
Incorrect fluid level
Add fluid to the proper level. Refer to
Transmission Fluid Check.
Sticking valves in control valve body
assembly
Rebuild the control valve body assembly.
Refer to Control Valve Body Replacement.
2008 Chevrolet Silverado 1500
2008 TRANSMISSION Automatic Transmission - Allison - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra &
Silverado