Chevrolet Silverado / GMC Sierra. Service manual — part 1406

Fig. 27: Identifying Cracked Inner Race
Courtesy of GENERAL MOTORS CORP.

Cracked race due to improper fit, cocking, or poor bearing seats. Replace the bearing. Correct
bearing seats.

Fatigue Spalling

2008 Chevrolet Silverado 1500

2008 Driveline/Axle Rear Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Fig. 28: Identifying Fatigue Spalling
Courtesy of GENERAL MOTORS CORP.

Flaked surface metal that results from fatigue. Replace the bearing. Clean all related parts.

Brinelling

2008 Chevrolet Silverado 1500

2008 Driveline/Axle Rear Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Fig. 29: Identifying Brinelling
Courtesy of GENERAL MOTORS CORP.

Surface indentations in the race way caused by the rollers under impact loading or caused from
vibration while the bearing is not rotating. Replace a rough or noisy bearing.

REAR AXLE LUBRICANT LEAK DIAGNOSIS

Rear axle lubricant leaks can occur at the following locations:

Axle tube to differential carrier housing joint

Axle shaft oil seal

Axle housing porosity

Differential housing cover gasket

2008 Chevrolet Silverado 1500

2008 Driveline/Axle Rear Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Drain plug

Fill plug

Pinion yoke oil seal

Vent tube

Determining the Cause

While most rear 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 the 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.

Gaskets

A leak at a gasket is usually caused by a poor fit of the components on each side of the gasket
surface. Inspect each component for distortion and for nicks or gouges that may prohibit the
gasket from sealing properly.

Rear Axle Housing

Rear axle housing lubricant leaks usually occur at the following locations:

Drain Plug

2008 Chevrolet Silverado 1500

2008 Driveline/Axle Rear Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado