Gm Spo Group Numbers; Diagnostic Information And Procedures; Noise Diagnosis - GMC chervolet camaro 1999 Service Manual

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Driveline/ Axle
Rear Drive Axle 4~23
GM SPO Group Numbers
Application
Axle Shaft
Differential Carrier
Drive Pinion
Inner Bearing
Oil Seal and Bearing
Outer Bearing
Pinion Flange
Rear Axle
Rear Cover and Gasket
Diagnostic Information and Procedures
Noise Diagnosis
Many noises that are reported c:J.S coming from the
rear axle actually originate from other components:
• The tires and wheels
• The road surfaces
• The wheel bearings
• The engine
• The transmission
• The muffler
• The body
Thoroughly inspect for the source of the noise before
disassembling the rear axle. Noise that originates
in other places cannot be corrected by adjustment or
replacement of rear axle components. The rear
axle differential gears are not absolutely quiet (like any
other mechanical devices). The rear axle differential
gears should be accepted as commercially quiet
unless some abnormal noise exists.
Use the following procedure in order to inspect for
axle noise under standard conditions:
1. Measure the rear axle lubricant in order to ensure
the correct level.
2. Drive the vehicle far enough in order to thoroughly
warm up the rear axle lubricant. ,
Select a level asphalt road, which reduces tire
noise and body drumming.
3. Note the speed at which the noise occurs.
4. Stop the vehicle.
5. Determine if the exhaust muffler roar or other
engine conditions cause the noise:
5.1 . Place the transmission range selector lever
iri NEUTRAL
5.2. Run the engine slowly up and down
through the engine speeds that correspond
to the speed at which the noise was
most pronounced.
GM SPO Group Number
5.000
5.000
5.000
5.000
5.000
5.000
5.000
5.000
5.000
6. Determine if the tires cause the noise:
6.1. Temporarily inflate all of the tires to
approximately 345 kPa (50 psi).
This will alter the noise caused by the tires,
but will not affect the noise made by the
rear axle.
6.2. Test drive the vehicle. Coast at speeds
under 48 km/h (30 mph).
The following characteristics of tire and rear
axle noise may help in determining if the
tires cause the noise:
• Rear axle noise usually stops when the
vehicle is coasting at speeds under
48 km/h (30 mph).
• Tire noise usually continues. The tone of
the tire noise becomes lower as the
speed of the vehicle is reduced.
• Rear axle noise usually sounds different
during driving and during coasting. Tire
noise remains the same during
driving and during coasting.
• Exhaust and axle noises change during
sudden acceleration and deceleration.
Tire noise remains constant during
sudden changes in vehicle speed.
• Tire noise is the most noticeable at the
speeds of 32-48 km/h (20-30 mph).
• Tire noise changes on different road
surfaces, but rear axle noise does
not change. Drive the vehicle over
smooth pavement or dirt roads
(not gravel) with the tires at normal
pressure. Tire noise will noticeably
change, or will disappear and reappear
with the road surface.

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