GMC chevrolet camaro 2000 Service Manual page 85

0-74 Vibration Diagnosis and CorrecUon
Vibration
Vibration is the repetitive motion of an object, back
and forth, or up and down. The following conditions
cause most vehicle vibrations:
.. A rotating component
" The engine combustion process firing impulses
Rotating components will vibrate with excessive
imbalance .or runout. During vibration diagnosis, the
amount of allowable imbalance or runout should
be considered a toleran_ce and not.a specification. In
other words, the less imbalance or runout the better.
A vibration concern will occur when the firing impulses
of the engine are. not properly isolated from the
passenger compartment.
A vibrating component operates at a consistent rate
(km/h, mph, or RPM). Measure the rate of vibrati_on in
question. When the rate/speed is determined, relate the
vibration to a component that operates at an equal
rate/speed in order to pinpoint the source. Vibrations
also tend to transmit through the body structure to other
components. Therefore, just because the seat vibrates
doesn't mean the source of the vibration is in the seat.
Vibrations consist of the following three elements:
• The source - the cause of the vibration
• The transfer path - the path the vibration travels
through the vehicle
• The responder - the component where the
vibration is felt
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In the preceding figure, the source of the vibration is
the unbalanced tire. The transfer path is the route
the vibrations travels through the vehicle's suspension
system into the steering column. The responder is
the steering wheel, which the customer reports
as vibrating. Eliminating any one of these three
elements will usually correct the condition. Decide,
from the gathered information, which element makes
the most sense to repair. Adding a brace to the
steering column may keep the steering wheel from
vibrating, but adding a brace is not a practical solution.
The most direct and effective repair would be to
properly balance the tire.
General-Jnformation
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Vibration· can also produce hoise. As an· example,
consider a vehicle that has an exhaust pipe whichjs
grounded to the frame. The source of the vi_bration ·
is the engine firing impulses traveling through ·
the exhaust. The transfer path is a grounded or
bound-up exhaust hanger. The responder is the frame.
The floor panel vibrates, acting as a large speaker,
which produces noise. The best repairwould be
to eliminate the transfer path. Aligning the exhaust
system and correcting the grounded condition at 1he
frame would eliminate the transfer path.
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