GMC chervolet camaro 1999 Service Manual page 57

0-54 Vibration Diagnosis and Correction
5. If the vibration still exists, perform the
following steps:
5.1. Remove the rotors/drums.
5.2. Run the vehicle back to speed.
6. If the vibration is eliminated, perform the
following steps:
6.1. Remove the rotors/drums one at a time.
6.2. Perform the vibration test for each
rotor/drum.
6.3. Replace the rotor/drum that is causing the
imbalance.
6.4. Inspect the balance of the new rotor/drum.
Checking Rotor/Drum Imbalance (Off-Vehicle)
1. Measure the diameter and the width of the
rotor/drum.
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2. Mount the rotor/drum on a balancer in the same
manner as a wheel.
Important: You can only inspect the rotors/drums for
static imbalance. Ignore the dynamic imbalance
reading.
3. Inspect for static imbalance.
4. If the rotor/drum shows imbalance, replace the
rotor/drum.
5. Inspect the balance of the new rotor/drum before
you install the rotor/drum on the vehicle.
General Information
Driveline Vibration Analysis
The following components are possible sources
of driveline vibration:
• The transmission output shaft
• The propeller shaft(s)/driveshaft(s)
• The pinion yoke/flange (2)
• The pinion gear
The above components are either bolted or splined
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together. Therefore, all of the components rotate at the (
same speed, vibrate at the same frequency, and
have the same symptoms.
Driveline vibrations may relate either to the first order
or to the second order of driveline rotation. Driveline
vibrations are always related to the speed of the
vehicle. The vibration is often related to torque. If the
vibration is worse or only noticeable when
accelerating, decelerating, or crowding the throttle, the
vibration is related to the torque. In this case, the
vibration will always occur at the same speed.
If a vibration is sensitive both to torque and to speed,
the driveline is the probable cause. Tire/wheel ·
vibrations are speed-sensitive, but not torque-sensitive.
First-Order Driveline Vibration Symptoms
The following symptoms may indicate first-order
driveline vibration:
• The vibration is related to vehicle speed.
• The vibration is torque sensitive.
• A boom or moan noise is present.
• The vibration occurs commonly above 72 km/h
(45 mph), but possibly at speeds as low as
48 km/h (30 mph).
• The roughness or buzz vibration is felt in the seat,
the floor or the steering wheel.
• The corresponding frequency on the EVA equals
first-order driveline rotation (25-60 Hz), (
depending on the speed of the vehicle and the
ratio of the axle. Refer to Matching Frequency to
Component RPM in order to obtain the rotation
speed of the propeller shaft.