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100-04-5
Noise, Vibration and Harshness
100-04-5
DIAGNOSIS AND TESTING
Noise Conditions
Gear noise is typically a howling or whining due
to gear damage or incorrect bearing preload. It
can occur at various speeds and driving
conditions, or it can be continuous.
Chuckle is a particular rattling noise that sounds
like a stick against the spokes of a spinning
bicycle wheel. It occurs while decelerating from
64 kmlh (40 mph) and can usually be heard all
the way to a stop. The frequency varies with
vehicle speed.
Knock is very similar to chuckle, though it may
be louder and occurs on acceleration or
deceleration. The teardown will disclose what
has to be corrected.
Clicking, popping or grinding noises may be caused
by the following:
worn, damaged or incorrectly installed wheel
bearing, suspension or brake component.
Check and rule out tires, exhaust and trim items
before disassembling the transmission to diagnose
and correct gear noise.
The noises described under Road Test usually
(
have specific causes that can be diagnosed by
observation as the unit is disassembled. The initial
clues are the type of noise heard on the road test
and driving conditions.
Vibration Conditions
Vibration at highway speeds may be caused by
the following:
out-of-balance front or rear wheels.
out-of-round tires.
Shudder or vibration during acceleration may be
caused by the following:
damaged powertrainldrivetrain mounts.
excessively high constant velocity (CV) joint
operating angles caused by incorrect ride height.
Check ride height, verify correct spring rate and
check items under inoperative conditions.
Road Test
I
A gear-driven unit will produce a certain amount
of noise. Some noise is acceptable and may be
audible at certain speeds or under various driving
conditions, as on a newly paved asphalt road. The
slight noise is in no way detrimental and must be
considered normal.
The road test and customer interview (if available)
provide information needed to identify the condition
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and give direction to the correct starting point for
diagnosis.
1. Make notes throughout the diagnosis routine.
Make sure to write down even the smallest bit
of information, because it may turn out to be the
most important.
2. Do not touch anything until a road test and a
thorough visual inspection of the vehicle have
been carried out. Leave the tire pressures and
vehicle load just where they were when the
condition was first observed. Adjusting tire
pressures, vehicle load or making other
adjustments may reduce the condition(s)
intensity to a point where it cannot be identified
clearly. It may also inject something new into
the system, preventing correct diagnosis.
3. Make a visual inspection as part of the
preliminary diagnosis routine, writing down
anything that does not look right. Note tire
pressures, but do not adjust them yet. Note
leaking fluids, loose nuts and bolts, or bright
spots where components may be rubbing
against each other. Check the load space for
unusual loads.
4. Road test the vehicle and define the condition
by reproducing it several times during the road
test.
5. Carry out the Road Test Quick Checks as soon
as the condition is reproduced. This will identify
the correct diagnostic procedure. Carry out the
Road Test Quick Checks more than once to
verify they are providing a valid result.
Remember, the Road Test Quick Checks may
not tell where the concern is, but they will tell
where it is not.
Road Test Quick Checks
1. 24-80 kmlh (1 5-50 mph): with light acceleration,
a moaning noise is heard and possibly a
vibration felt in the front floor panel. It is usually
worse at a particular engine speed and at a
particular throttle setting during acceleration at
that speed. It may also produce a moaning
sound, depending on what component is
causing it. REFER to Tip-in Moan in the
Driveline Noise and Vibration Symptom Chart.
2006.0 Fiesta
1212006
G37349en
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