100-04-37
Noise, Vibration and Harshness
100-04-37
DIAGNOSIS AND TESTING
E859 EN
02/2001 2002 Bantam
Noise, Vibration and Harshness (NVH)
Inspection and Verification
1. Verify the customer concern by operating the
vehicle to duplicate the condition.
2. Visually inspect the vehicle to determine any
obvious causes of the concern(s).
3. If the inspection reveals obvious concern(s)
that can be readily identified, repair as
necessary.
4. If the concern(s) remains after the inspection,
determine the symptom(s) and
How To Use This Diagnostic Procedure Section
• Noise, vibration and harshness concerns
have become more important as vehicles
have become more sensitive to these
vibrations. This section is designed to aid in
identifying these situations.
• The section provides diagnostic procedures
based on symptom. If the condition occurs at
high speed, for instance, the most likely place
to start is under High Speed Shake.
• The road test procedure will tell how to sort
the conditions into categories and how to tell
a vibration from a shake.
• A series of Road Test Quick Checks is
provided to make sure that a cause is either
pinpointed or eliminated.
• Use the Vehicle Road Test Evaluation form to
record road test results.
• Use the Glossary to become familiar with the
terms.
• Name the condition, proceed to the
appropriate section and locate the correct
diagnosis. When the condition is identified,
the job is partly done.
• Follow the diagnostic procedure as outlined.
• Quick Checks are described within the step,
while more involved tests and adjustments
are outlined in Service Procedures and
Adjustments.
• Always follow each step exactly and make
notes to recall important findings later.
Customer Interview
The road test and customer interview (if
available) provide information that will help
identify the concern and will provide direction to
the correct starting point or diagnosis.
• Use the Customer Concern Evaluation form
to record customer concerns.
Identifying the Condition
Noise, vibration, and harshness (NVH) usually
occur in four areas:
• Tires
• Engine accessories
• Suspension
• Driveline/driveshaft centre bearing
NOTE:
If the driveshaft centre bearing cap is
removed, a new bearing cap must be installed.
It is important, therefore, that an NVH concern be
isolated into its specific areas as soon as
possible. The easiest and quickest way to do this
is to
carry out the Road Test as outlined.
Noise Diagnostic Procedure
Non-Axle Noise
The five most common sources of non-axle noise
are exhaust, tires, roof racks, trim mouldings and
transaxle.
Therefore, make sure that none of the following
conditions are the cause of the noise before
proceeding with a driveline teardown and
diagnosis.
• In certain conditions, the pitch of the exhaust
may sound very much like gear noise. At
other times, it can be mistaken for a wheel
bearing rumble.
• Tires, especially snow tires, can have a high
pitched tread whine or roar, similar to gear
noise. Radial tires, to some degree, have this
characteristic. Also, any non-standard tyre
with an unusual tread construction may emit a
roar or whine-type noise.
• Trim and mouldings can also cause whistling
or whining noise.
