GMC chervolet camaro 1999 Service Manual page 53

0-50 Vibration Diagnosis and Correction
Classifying the Vibration
The next step after road testing the vehicle is to
identify the frequency of the duplicated and abnormal
vibration. Use the EVA in order to measure the
frequency. If the EVA is not available, observe how
the vibration feels or sounds. The majority of vibrations
will fit into one of the following categories.
• Vibrations that can be felt:
- Shake
- Roughness
- Buzz
- Tingling
• Vibrations that make noise:
- Boom
- Moan and groan
- Howl
- Whine
Vibrations That .Can Be Felt
Shake
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The shake is a low frequency vibration, typically
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5-20 Hz. The shake is sometimes seen in the steering
wheel, the seat, or the console. The best description
is the feeling from an out-of-round or unbalanced
tire. Customers may refer to a shake in one of the
following terms:
• Shimmy
• Wobble
• Shudder
• Waddle
• Hop
General Information
In most cases, shake is caused by damage or wear to
the following components:
• The tires
• The wheels
• The brake rotors {vehicle-speed sensitive)
• The steering tie rod ends
• The suspension ball joints
• The engine {engine-speed sensitive)
Roughness
Roughness is a vibration with a slightly higher
frequency than the shake, usually 20-50 Hz.
Roughness is similar to the feeling you get from
holding a jigsaw.
Buzz
Buzz is slightly higher in frequency: 50-100 Hz. A
buzz is similar to the feel of an electric razor. You may
feel it in your hands through the steering wheel, in
your feet through the floor, or in the seat. Inspect the
following components for a possible cause:
• The exhaust system
• The A/C compressor
• The engine
Tingling
This is the highest vibration frequency that you can
feel. Tingling may sometimes produce a pins and
needles sensation. Customers may say the vibration
creates numbness in their hands or feet.
Vibrations That Make Noise
Boom
Boom is a low frequency interior noise of 20-SO Hz.
Sometimes the customers complain of a pressure
in their ears. Examples of similar noises include
a bowling ball rolling down an alley, deep thunder, or
a bass drum.
A customer may use the following words to
describe boom:
• Droning
• Growling
• Moaning
• Roaring
• Rumbling
• Humming
Boom may be accompanied by a perceptible vibration
{roughness).
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