CS35 2013.04
1.1.5-7 1.1.5-7Noise, Vibration and Harshness
Symptom Diagnosis and Testing
Inspection and Verification
1. Start the vehicle to reshow the malfunction,
verify the customer concern.
2. Visually inspect for obvious signs for
malfucntion.
3. If an obvious cause for an observed or
reported concern is found, correct the cause
(if possible) before proceeding to the next
step.
4.
If
the
conce
r
n is
not
visua
lly evide
n
t,
verify
th
e sympt
o
m a
nd refer
to the
symptom ch
art.
How to Use This Diagnosis
Procedure Section
Noise, vibration an
d harshness (NVH)
concern
has become more important as vehicles have
become more sensitive to these vibrations. This
section is designed
t
o
aid in iden
tifying th
ese con-
cerns
.
This section is used to assort and identify these
problems. For example, if the condition occurs at
high speed, for instance, the most likely place to
start is under shake and vibration while driving.
The road test procedure can classify the condi-
tions a
nd id
entif
y the
vib
ration
from shaking
.
A series of
Road T
e
st
Qu
ick Inspect
s
are
pro-
vided to make sure that a cause is either pin-
pointed or eliminated.
Name th
e condition
, p
r
ocee
d to
th
e a
ppropriate
section a
nd
locate t
he correct d
i
agno
sis. W
hen
the condition is identified, the job is partly done.
Follow the diagnostic procedure as outlined.
Quick Inspects are described within the steps,
while more involved tests and adjustments are
out
line
d
in
Gene
ral Procedure
s
.
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 con-
cern and will provide direction to the correct start-
ing point for diagnosis.
Identify the Condition
NVH usu
a
lly occur in four
areas:
•Tire
•
E
ngine
accessories
•
S
uspe
nsion
•
D
rive
line
It is important, therefore, that an NVH concern be
isolated into it
s sp
ecific
area(s) as soo
n
as possi-
ble. T
he ea
sie
s
t
and q
u
ickest way to
do t
h
is
is to
carry
out th
e Road T
e
st as outlined.
T
o
assist
in
the diagnosis and testing procedure(s), use a
suit
able appro
v
ed
NVH diagnosis test
er
.
Noise Diagnostic Procedure
Non-Axle Noise
The five most common sources of non-axle noise
are
exhaust,
tires, roof racks, trim
p
ane
ls and
tra
n
smission
.
Therefore, make sure that none of the following
conditions are
the cause of
the no
ise
before
pro-
ceeding 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
mist
aken
for a wheel bearing rumble.
• Tires, especially snow tires, can have a
high
pitch
ed tread whine
or roar
,
similar
to gear noise. Radial tires may have this
cha
r
acte
ristic. Also, an
y non
-st
andard
tire
with an unusual tread construction may
emit a roa
r
or whin
e noise.
•
T
rim p
a
n
e
ls can a
l
so
cause whistling or
whining noise.
•
C
lunk
may be a
met
a
llic noise heard
when the a
u
toma
tic
tra
n
sa
xle is eng
aged
in "R" (REVERSE) or "D" (DRIVE) or it
may o
ccu
r when
the
throt
t
le
is
app
lied
or
released. It is caused by backlash
somewhere in the driveline.
•
B
earin
g rumble sound
s like marbles
being tumbled. This condition is usually
caused by a damaged wheel bearing.
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