GMC 1982 Light Duty Truck Service Manual page 421

NOISE
The most essential part of rear axle service, as with any
mechanical repair, is proper diagnosis of the problem, and,
in axle work one of the most difficult areas to diagnosis is
noise. Locating a broken axle shaft, or broken differential
gear, presents little or no problem, but, locating and
isolating axle noise can be an entirely different matter.
D egree of Noise
Any gear driven unit, and especially an automotive
drive axle where engine torque multiplication occurs at a
Fig. 4B-5a--Rockwell 12" Ring Gear Axle-11,000# Capacity
DIAGNOSIS
90° turn in the drive line, produces a certain amount of
noise. Therefore, an interpretation must be made for each
vehicle to determine whether the noise is normal or if a
problem actually exists. A normal amount of noise must be
expected and cannot be eliminated by conventional repairs
or adjustment.
Acceptable noise can be defined as a slight noise heard
only at a certain speed or under unusual or remote
conditions. For example, this noise tends to reach a "peak"
at speeds from 40 to 60 miles per hour (60 to 100 km /h)
depending on road and load conditions, or on gear ratio and
tire size. This slight
REAR A X LE 4 B -7
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noise is in no way