Chevrolet Silverado / GMC Sierra. Service manual — part 1392

Fig. 243: Identifying Drive Side Toe - Coast Side Heel Contact Pattern
Courtesy of GENERAL MOTORS CORP.

Condition

The pinion depth is incorrect. The drive pinion is too close to the ring gear.

Correction

Adjust the pinion depth of drive pinion. Refer to Pinion Depth Adjustment.

Drive Side Heel - Coast Side Heel Contact Pattern

2008 Chevrolet Silverado 1500

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

Fig. 244: Identifying Drive Side Heel - Coast Side Heel Contact Pattern
Courtesy of GENERAL MOTORS CORP.

Condition

The backlash is incorrect. The ring gear is too far away from the drive pinion.

Correction

Decrease the backlash. Move the ring gear closer to the drive pinion by adjusting the side bearing
adjuster sleeves. Refer to Backlash Inspection and Adjustment.

Drive Side Toe - Coast Side Toe Contact Pattern

2008 Chevrolet Silverado 1500

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

Fig. 245: Identifying Drive Side Toe - Coast Side Toe Contact Pattern
Courtesy of GENERAL MOTORS CORP.

Condition

The backlash is incorrect. The ring gear is too close to the drive pinion.

Correction

Increase the backlash. Move the ring gear away from the drive pinion by adjusting the side
bearing adjuster sleeves. Refer to Backlash Inspection and Adjustment.

DESCRIPTION AND OPERATION

FRONT DRIVE AXLE DESCRIPTION AND OPERATION

Selectable Four Wheel Drive (S4WD) Front Axle Description and Operation

The Selectable Four Wheel Drive (S4WD) Front Axle consist of the following components:

Differential Carrier Housing

Differential Assembly

Output Shafts (Left and Right Side)

Inner Axle Shaft Housing

2008 Chevrolet Silverado 1500

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

Inner Axle Shaft (Right Side)

Clutch Fork

Clutch Fork Sleeve

Electric Motor Actuator

The front axle on Selectable Four Wheel Drive model vehicles uses a central disconnect feature
in order to engage and disengage the front axle. When the driver engages the 4WD system, the
Transfer Case Control Module sends a signal to the electric motor actuator to energize and extend
the plunger inside. The extended plunger moves the clutch fork and clutch fork sleeve across the
inner axle shaft and the clutch fork shaft and locks the two shafts together. The locking of the two
shafts allows the axle to operate in the same manner as a semi-floating rear axle. A propeller shaft
connects the transfer case to the front axle. The differential carrier assembly uses a conventional
ring and pinion gear set to transmit the driving force of the engine to the wheels. The open
differential allows the wheels to turn at different rates of speed while the axle continues to
transmit the driving force. This prevents tire scuffing when going around corners and premature
wear on internal axle parts. The ring and pinion set and the differential are contained within the
carrier. The axle identification number is located on top of the differential carrier assembly or on
a label on the bottom of the right half of differential carrier assembly. The drive axles are
completely flexible assemblies consisting of inner and outer constant velocity CV joints protected
by thermoplastic boots and connected by a wheel drive shaft.

Full-Time Four Wheel Drive (F4WD) Front Axle Description and Operation

The Full-Time Four Wheel Drive (F4WD) Front Axle consist of the following components:

Differential Carrier Housing

Differential Assembly

Output Shaft (Left Side)

Inner Axle Shaft Housing

Inner Axle Shaft (Right Side)

The front axle on Full-Time Four Wheel Drive model vehicles does not have a central disconnect
feature in order to engage and disengage the front axle. The left and right axle shafts are
connected directly to the differential case assembly. This allows the axle shafts and the propeller
shaft to spin continuously. The transfer case controls the amount of torque applied to the front
axle. The remaining components are the same as the selectable four wheel drive axle.

SPECIAL TOOLS AND EQUIPMENT

2008 Chevrolet Silverado 1500

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