GMC chevrolet camaro 2000 Service Manual page 71

0-60 Vibration Diagnosis and Correction
4. Continue the trial and error procedure using
different weights in different locations until
you achieve the best balance.
5. If more than three clamps aligned in the same
position are required, replace the propeller shaft.
6. If you are able to reduce the vibration in the stall,
but are unable to eliminate the vibration
completely, road test the vehicle. A slight vibration
that is noticeable in the stall may not be
noticeable on the road.
First-Order Driveline Vibration Analysis
(Torque Sensitive)
If the following conditions are true, the internal rear
axle components are the probable cause of the
vibration:
• The vehicle has a vibration that is equal to
first-order driveline rotation, and the vibration is
not present you test the vehicle in the stall.
• You were able to correct the vibration in the stall,
but the vibration returned during the road test.
Internal rear axle vibrations may be aggravated by the
load of the vehicle working against the ring and
pinion gear seat.
Since the propeller shaft and the pinion gear are
bolted together through the pinion flange, the propeller
shaft and the pinion gear operate at the same
speed. Vibration in the pinion gear will therefore have
the same frequency and symptoms as the
propeller shaft.
In order to isolate the vibration to the pinion gear, use
the following procedure:
1. Raise the vehicle to curb height. Support the
vehicle on a hoistor on safety stands. Refer
to Lifting and Jacking the Vehicle in General
Information.
2. Remove the tire and wheel assemblies. Refer to
Tire and Wheel Removal and Installation in Tires
and Wheels.
3. Touch the pinion nose or hold the EVA vibration
sensor up to the pinion nose.
4. With the aid of another technician, accelerate and
decelerate the vehicle through the speed range at
which the vibration was noticed during the
road test.
Example
• If the vibration was originally noticed at
88 km/h {55 mph), accelerate from 72 km/h
{45 mph) to 107 km/h (65 mph). Then
decelerate from 107 km/h (65 mph) back to
72.km/h (45 mph).
• Repeat the above step and remember whether
or not the pinion nose vibrates under load
during acceleration and/or deceleration,
General Information
If the vibration does not occur during the above
procedure, install the brake drums and the tire/wheel I
assemblies, adding additional load on the system. \
Then repeat the above test.
Ensure that both axle shafts rotate at the same speed.
The differential may mask a vibration when one tire
is spinning faster than the other tire. Adjust the brakes
in order to correct unequal tire rotation speed.
If you are unable to reproduce the vibration in the
stall, apply the brake lightly in order to load the system
further. Maintain the vehicle speed at which the
vibration was noticed. Do not overheat the brakes.
If the pinion nose vibrates under acceleration and/or
deceleration, and the other driveline components are
eliminated as the cause of the vibration, then one of the
following conditions may cause the vibration:
• A high spot on the pinion gear
• A bent pinion stem
.. A cocked pinion bearing
• An improper axle housing bore
Anything that effects the pinion gear and how the
pinion gear contacts the rotating ring gear may
contribute to a first-order, torque-sensitive driveline
vibration. The only.way to correct the.condition
is to replace the faulty components. In most cases,
you must replace the ring and pinion gear set and the (
related bearings. In some cases, you must replace
the axle housing. Complete a close-up visual
inspection for damage or unusu.al wear in order to
measure or identify the specific faulty component.
It is possible to isolate an internal axle vibration. Install
a known good axle assembly from a stock unit.
Verify that the known good axle assembly does not
have a vibration problem ..
Once you correct the internal axle problem, road test
the vehicle.· Inspect the vehicle· for vibration.
Balance the driveline, as necessary, in order to
eliminate any remaining vibration.