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Chevrolet Silverado / GMC Sierra. Manual - part 1327
FOUR-WHEEL DRIVE DOES NOT DISENGAGE
1
Diagnostic Starting Point - Front Drive
Axle.
Is the system operating properly?
Test the system
Go to Step 2
2
1. Raise the vehicle. Refer to Lifting and
Jacking the Vehicle .
2. Remove the actuator motor. Refer to
Front Drive Axle Actuator
Replacement.
3. Using a brass drift, apply pressure to the
clutch fork.
4. Turn the right wheel to align the clutch
gears.
While turning the right wheel, does the left
wheel turn in the opposite direction?
Test the system
Go to Step 3
3
1. Remove the inner axle shaft and housing
assembly. Refer to Front Drive Axle
Inner Shaft and Inner Shaft Housing
Replacement (8.25 F4WD Axle) or
Front Drive Axle Inner Shaft and Inner
Shaft Housing Replacement (8.25
S4WD and 9.25 Axles).
2. Inspect the following:
Clutch Fork
Clutch Sleeve
Clutch Gear
Clutch Return Spring
Repair as needed.
Did you complete the repair?
Test the system
System OK
IMPORTANT: Before performing the following diagnostic procedure, ensure
that all electrical diagnostic procedures have been performed and
there are no DTCs.
2008 Chevrolet Silverado 1500
2008 Driveline/Axle Front Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
FRONT AXLE LUBRICANT LEAK DIAGNOSIS
Front axle lubricant leaks can occur at the following locations:
Step
Action
Yes
No
1
Confirm operation of system. Refer to
Diagnostic Starting Point - Front Drive
Axle.
Is the system operating properly?
Test the system
Go to Step 2
2
1. Raise the vehicle. Refer to Lifting and
Jacking the Vehicle .
2. Remove the actuator motor. Refer to
Front Drive Axle Actuator
Replacement.
3. Using a brass drift, apply pressure to the
clutch fork.
4. Turn the right wheel to align the clutch
gears.
While turning the right wheel, does the left
wheel turn in the opposite direction?
Test the system
Go to Step 3
3
1. Remove the inner axle shaft and housing
assembly. Refer to Front Drive Axle
Inner Shaft and Inner Shaft Housing
Replacement (8.25 F4WD Axle) or
Front Drive Axle Inner Shaft and Inner
Shaft Housing Replacement (8.25
S4WD and 9.25 Axles).
2. Inspect the following:
Clutch Fork
Clutch Sleeve
Clutch Gear
Clutch Return Spring
Repair as needed.
Did you complete the repair?
Test the system
System OK
2008 Chevrolet Silverado 1500
2008 Driveline/Axle Front Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Axle shaft oil seals
Differential carrier assembly mating surface
Drain plug
Fill plug
Inner axle tube assembly to differential carrier assembly mating surface
Pinion yoke oil seal
Vent tube and/or connector
Determining the Cause
While most front axle leaks may be easy to find, determining the cause may not be. A thorough
inspection of the area around the leak may assist in determining the cause of the leak.
Oil Seals
Lubricant leaks from a oil seal may be caused by any of the following:
An improperly installed seal
A distorted seal
A worn seal
A worn shaft
A brittle seal lip
A hardened seal lip
To determine the actual cause of the leak, clean the area around the leak. Observe the area of the
leak and determine if the seal or another component is causing the leak. A worn seal surface will
cause a leak at the sealing lip while a misaligned seal or a seal installed into a housing with an
excessive bore will cause the seal to leak at the outside surface of the seal. Hardened or cracked
seal lips usually indicate the axle is operating beyond the normal temperature limits for the axle.
A seal whose sealing surface has been nicked or cut may indicate that the shaft has a rough,
burred, or gouged surface and will need to be inspected before the seal can be replaced.
Sealing Surfaces
Front axles are assembled using specific sealers. A leak at a surface sealed with sealant is usually
caused by a poor fit of the components but can also be caused by the use of the wrong sealant.
When correcting a sealant leak, inspect each component for distortion and for nicks or gouges
that may prohibit the sealant from sealing properly and when re-assembling the component, use
the proper sealant.
2008 Chevrolet Silverado 1500
2008 Driveline/Axle Front Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Differential Carrier Assembly
Lubricant leaks at the differential carrier assembly can occur at the following locations:
Drain plug
Fill plug
Vent tube
Drain and fill plug leaks are usually caused by a loose plug. A vent tube leak can be cause by a
loose fitting vent hose or by a vent tube assembly whose interior shield is stuck in the upside
down position. Inspect the vent plug's interior shield for unrestricted movement, repair or replace
the plug as necessary. Drain or fill plug leaks can be repaired by either tightening the plug or by
using an approved sealer on the threads on the plug.
REPAIR INSTRUCTIONS
FRONT AXLE LUBRICANT REPLACEMENT
Removal Procedure
1. Raise the vehicle. Refer to Lifting and Jacking the Vehicle .
2. Remove the engine shield, if equipped. Refer to Engine Shield Replacement .
3. Clean the area around the front axle fill plug and the drain plug.
4. Remove the fill plug.
2008 Chevrolet Silverado 1500
2008 Driveline/Axle Front Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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