1.1.5-8
CS35 2013.04
1.1.5-8Noise, Vibration and Harshness
Noise Conditions
•
G
ear noise is typically
a
h
o
wling
o
r
whin
ing
due to
gear
dama
ge or
incorrect
bearing preload. It can occur at various
speeds
a
nd
d
r
iving con
d
itions, or it can
be continuous.
•
C
huckle
is a p
a
rticular rattling noise tha
t
sounds
like
a stick again
s
t the spo
k
es
o
f
a
spinnin
g
bicycle
wheel. It
occurs
while
decelerating from 64 km/h and can
usually be heard all the way to a stop.
The
freque
ncy varies with ve
hicle speed.
• Knock is very similar to chuckle, though it
may be louder and occurs on
acceleration or decelerat
ion. The
tea
r
down will disclose
wh
at has to be
corrected.
Clicking, Popping or Grinding Noises
May Be Caused by The Following:
• Worn, damaged or incorrectly installed
wheel bearing, susp
ension or
brake
compo
nent.
•
I
nspect an
d rule o
u
t tires,
exhaust and
trim items before disassembling the
transmission to diagnose and correct
gear noise.
Vibration Conditions
Vibration at highway may be caused by the fol-
lowing
:
•
O
ut-of-ba
lance fron
t or rear
wh
eels.
•
O
ut-of-round tires.
Sh
udder or
vibra
tion during
a
c
celerat
i
on may
be
caused by the
following:
•
D
amaged p
o
wertrain
/drivetrain mo
unt
s
•
E
xcessively hig
h
con
s
t
ant velo
city (CV)
jo
int op
eratin
g angles caused by incorrect
ride height. Inspect ride height, verify
correct
sp
ring rate and che
ck ite
m
s unde
r
in
operat
ive cond
itio
ns.
Road Test
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
detriment
al an
d must
be considered normal.
The road test and customer interview (if available)
provide information needed to identify the condi-
tion 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
import
ant.
2.
Do not tou
c
h an
ything until a road
t
e
st an
d a
thoro
ugh visual inspecti
on of the ve
hicle have
bee
n
carried out. Lea
ve the tire pressures
and
vehicle loa
d
just where the
y
we
re
whe
n
the condition was first observed. Adjusting
tire pressures, vehicle load or making other
adjustment
s
may re
duce
the
condit
i
on(s)
intensity to a point where it cannot be
identified clearly. It may also inject something
new into th
e system, pre
v
enting correct
dia
gnosis.
3.
Ma
ke a
visual inspection
as
p
a
rt of th
e
preliminary diagnosis routine, writing down
anything that does not look right. Note tire
pressure
s, but do
not adjust the
m
yet
.
Not
e
lea
k
in
g fluids, loose
n
u
t
s
and bolt
s
, or brigh
t
spots where components may be rubbing
against each other. Inspect the load space for
unusual loads.
4. Road test the vehicle and define the condition
by reprodu
cing
it se
veral times du
ring th
e
road
test.
5. Carry out the Road Test Quick Inspects as
so
on as the condition
is reprodu
ced.
This will
identify the correct diagnostic procedure.
Carry ou
t
t
he road test quick ch
ecks mo
re
than once to verify they are providing a valid
result.
Remember
,
the
road
test q
u
ick
checks
ma
y no
t tell where
the concern is, bu
t they
will tell where it is not.
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