Chevrolet Silverado / GMC Sierra. Manual — part 1399
Locking Rear Axle Does Not Lock
Locking Rear Axle Locks in Turns
Locking Rear Drive Axle Chatters in Turns
Noise in Addition to Normal Clutch Engagement
SYMPTOMS - REAR DRIVE AXLE
Review the system and operation in order to familiarize yourself with the system functions. Refer
to Rear Drive Axle Description and Operation.
Rear Axle Noise
The proper diagnosis is an important part of rear axle repair. In axle work, one of the most
difficult conditions to diagnose is noise. Locating a broken axle shaft or broken differential gear
presents little or no problems, but locating and isolating axle noise can be an entirely different
matter.
Any gear driven unit, especially an automotive drive axle where the engine torque multiplication
occurs at a 90 degree turn in the driveline, produces a certain amount of noise. Therefore, an
interpretation must be made for each vehicle in order to determine where the noise is normal or if
a problem actually exists. A certain amount of noise must be expected and cannot be eliminated
by conventional repairs or adjustment.
Normal axle noise can be described as a slight noise heard only at a certain speed or under
unusual or remote conditions. For example, the noise tends to reach a peak at speeds from 60-100
km/h (40-60 mph) depending on road and load conditions, or on gear ratio and tire size. This
slight noise is in no way indicative of trouble in the axle assembly.
Driveline noises may confuse even the best technician. Vehicle noises coming from tires,
transmission, propeller shaft, universal joints, and front or rear wheel bearings are often mistaken
for axle noise.
Visual/Physical Inspection
Inspect the system for loose or missing fasteners.
Inspect the system for leaking components.
Inspect the system for obvious damage or conditions which may cause the symptom.
Symptom List
Refer to a system diagnostic procedure from the following list in order to diagnose the symptom:
2008 Chevrolet Silverado 1500
2008 Driveline/Axle Rear Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
Rear Drive Axle Noises
Noisy in Drive
Noisy When Coasting
Intermittent Noise
Constant Noise
Noisy on Turns
REAR DRIVE AXLE NOISES
Gear Noise
Gear noise or whine is audible from 32-89 km/h (20-55 mph) under 4 driving conditions:
Drive- Acceleration or heavy pull
Road Load-Vehicle driving load or constant speed
Float-Using enough throttle to keep the vehicle from driving the engine, the vehicle slows
down gradually but the engine still pulls slightly
Coast-Throttle is closed and the vehicle is in gear
Gear noise most frequently has periods where the noise is more prominent, usually between 48-64
km/h (30-40 mph) and 80-85 km/h (50-53 mph). Gear whine is corrected by either ring and
pinion gear replacement or adjustment, depending on the mileage of the gearset.
Bearing Noise
Faulty bearings produce a rough growl or grating sound, rather than the whine typical of gear
noise. Bearing noise/hum will pulsate at a constant vehicle speed. This indicates a bad pinion or a
bad rear axle side bearing. This noise can be confused with rear wheel bearing noise. Inspect and
replace the bearings and the affected components as required.
Rear Wheel Bearing Noise
A rough rear wheel bearing produces a noise which continues with the car coasting at low speed
and the transmission in neutral. The noise may diminish some when the brakes are gently applied.
The noise may also change when performing side-to-side maneuvers with the vehicle.
A rough/noisy rear wheel bearing can be heard by spinning the rear wheels by hand and listening
at the hubs for the noise. Inspect and replace the bearings and the affected components as needed.
Knock at Low Speeds
2008 Chevrolet Silverado 1500
2008 Driveline/Axle Rear Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
A low speed knock can be caused by a differential case side gear bore that has worn oversize.
Inspect the side gears and differential case and replace the components as necessary.
Backlash Clunk
Excessive backlash clunk under acceleration or deacceleration can be caused by any of the
following:
Worn differential pinion shaft
Worn differential pinion and/or side gear teeth
Worn thrust washers
Excessive clearance between the side gears and the axle shafts
Excessive clearance between differential side gears and the bore in the case
Excessive drive pinon and ring gear backlash
Inspect, adjust or replace the affected components as necessary.
NOISY IN DRIVE
Cause
Correction
DEFINITION: A noise heard during acceleration load.
Excessive pinion to ring gear
backlash
Adjust the pinion to ring gear backlash. Refer to Backlash
Adjustment (8.6 Inch Axle) or Backlash Adjustment
(10.5, 11.5 Inch Axles) or Backlash Adjustment (9.5 LD
Axle).
Worn pinion and ring gear
Replace the pinion and the ring gear. Refer to Drive Pinion
and Ring Gear Replacement (8.6, 9.5/9.5LD, and 11.5
Inch Axles) or Drive Pinion and Ring Gear Replacement
(10.5 Inch Axle).
Worn pinion bearings
Replace the pinion bearings. Refer to Drive Pinion Bearings
Replacement (8.6, 9.5, 11.5 Inch Axle) or Drive Pinion
Bearings Replacement (10.5 Inch Axle).
Loose pinion bearings
Adjust the pinion bearings preload. Refer to Pinion Depth
Adjustment (10.5 Inch Axle) or Pinion Depth Adjustment
(8.6, 9.5/9.5LD, and 11.5 Inch Axles).
Excessive pinion end play
Adjust the pinion end play. Refer to Pinion Depth
Adjustment (10.5 Inch Axle) or Pinion Depth Adjustment
(8.6, 9.5/9.5LD, and 11.5 Inch Axles).
2008 Chevrolet Silverado 1500
2008 Driveline/Axle Rear Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
NOISY WHEN COASTING
INTERMITTENT NOISE
Worn differential bearings
Replace the differential bearings. Refer to Differential Side
Bearings Replacement (All Except 9.75 Inch Axle).
Loose differential bearings
Adjust the differential bearing preload. Refer to Differential
Carrier Bearing Preload Adjustment (10.5 Inch, 11.5
Inch Axles) or Differential Carrier Bearing Preload
Adjustment (8.6 Inch Axle) or Differential Carrier
Bearing Preload Adjustment (9.5, and 9.5LD Inch Axles).
Excessive ring gear runout
Replace the ring gear. Refer to Drive Pinion and Ring Gear
Replacement (8.6, 9.5/9.5LD, and 11.5 Inch Axles) or
Drive Pinion and Ring Gear Replacement (10.5 Inch
Axle)
.
Low oil level
Fill the fluid level to specifications with the proper lubricant.
Refer to Rear Axle Lubricant Level Inspection (11.5 Inch
Axle) or Rear Axle Lubricant Level Inspection (8.6, 9.5
LD Axle) or Rear Axle Lubricant Level Inspection (10.5
Inch Axle).
Wrong or poor grade oil
Drain and refill the system with the proper lubricant. Refer to
Rear Axle Lubricant Replacement (8.6 Inch Axle) or
Rear Axle Lubricant Replacement (9.5 Inch LD Axle)
or
Rear Axle Lubricant Replacement (10.5 Inch Axle).
Bent axle housing
Replace the axle housing. Refer to Rear Axle Housing
Replacement (w/Rear Drum) or Rear Axle Housing
Replacement (w/Rear Disc ).
Checks
Action
DEFINITION: Noise is audible when slowing down and disappears when driving.
Worn pinion and ring gear
Adjust or replace the pinion and the ring gear. Refer to Drive
Pinion and Ring Gear Replacement (8.6, 9.5/9.5LD, and
11.5 Inch Axles) or Drive Pinion and Ring Gear
Replacement (10.5 Inch Axle).
Pinion and ring gear too
tight
Adjust the pinion and the ring gear backlash. Refer to
Backlash Adjustment (8.6 Inch Axle) or Backlash
Adjustment (10.5, 11.5 Inch Axles) or Backlash
Adjustment (9.5 LD Axle).
2008 Chevrolet Silverado 1500
2008 Driveline/Axle Rear Drive Axle - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado
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