Chrysler 1998 Viper RT/10 Owner's Manual page 123

SR
DIFFERENTIAL AND DR1WEL1NE
3 - 3
D I A G N O S I S A N D TESTING (Continued)
bearing is usually more pronounced d u r i n g a coast
condition. The drive pinion rear bearing noise is
more pronounced d u r i n g a drive condition. The drive
pinion bearings are r o t a t i n g at a higher rate of speed
t h a n the differential side bearings.
Side bearing noise w i l l usually produce a constant,
rough sound t h a t is much lower i n frequency t h a n
drive pinion bearing noise.
. Bearing noise can best be detected by road testing
the vehicle on a smooth road (black top). However, i t
is easy to mistake t i r e noise for bearing noise. I f a
doubt exists, the t i r e treads should be examined for
irregularities t h a t often causes a noise t h a t resem-
bles bearing noise.
FRONT WHEEL BEARING NOISE
Loose or rough front wheel bearings w i l l cause
noise t h a t can be confused w i t h rear axle noise; how-
ever, front wheel bearing noise does not change when
i t is compared d u r i n g drive and coast conditions.
Front wheel bearings can easily be tested for noise
by raising the vehicle and spinning the front wheels.
Also shake the front wheels to determine i f the bear-
ings are loose.
BACKLASH CLUNKING NOISE
A loud clunk noise upon acceleration and decelera-
t i o n could be caused by the following components (or
i n combination):
• Differential pinion mate gear shaft-to-differen-
t i a l case bore.
• Axle shaft splines-to-differential side gear
splines.
• Differential side gear hub-to-differential case
counter-bore.
• Differential side gears-to-pinion gears.
• Worn t h r u s t washers.
• Excessive r i n g gear backlash.
Measure the clearances, inspect the components
and replace as required (or, i f applicable, adjust to
specifications).
KNOCK AT LOW SPEEDS
Low speed knock is usually caused by either:
• Brinelled universal j o i n t spider
• Excessive differential side gear hub-to-counter-
bore clearance
Inspect and replace the universal j o i n t or the dif-
ferential case and side gear, as applicable.
GEAR NOISE (DRIVE PINION AND RING GEAR)
Abnormal gear noise is rare and, i f i t exists, is usu-
ally caused by scoring on the r i n g gear and drive pin-
ion. Scoring is the result of insufficient or incorrect
lubricant i n the carrier housing.
A b n o r m a l gear noise can be noticed easily because
i t produces a cycling tone. This tone w i l l be pro-
nounced w i t h i n a given speed range. The noise can
occur d u r i n g one or more o f the following drive con-
ditions:
• Drive
• Road load
• Float
• Coast
A b n o r m a l gear noise usually tends to peak w i t h i n
a narrow vehicle speed range or ranges. I t is usually
more pronounced between 30 to 40 m p h (48 to 64
km/h) and 50 to 60 m p h (80 to 96 km/h). W h e n objec-
tionable gear noise occurs, note the d r i v i n g condi-
tions and the speed range.
ENGINE AND TRANSMISSION NOISE
Occasionally noise t h a t appears to be from the dif-
ferential is actually caused by the engine or trans-
mission. To identify the true source of the noise, note
the approximate vehicle speed and/or R P M when the
noise is most noticeable. Stop the vehicle next to a
flat brick or cement w a l l (this w i l l help reflect the
sound). Place the transmission i n N E U T R A L . Then
vary the engine R P M slowly up and down t h r o u g h
the engine speed t h a t corresponds to the R P M noted.
I f a s i m i l a r noise is produced using this method, the
noise is being caused by the engine or transmission,
not the differential assembly.
PRE-DISASSEMBLY INSPECTION
A close inspection of the rear axle differential prior
to disassembly is important. I t can often reveal valu-
able information concerning the extent and type of
repairs or adjustments t h a t are necessary. This infor-
mation, combined w i t h the road test results, w i l l pro-
vide a basis for determining the degree of
disassembly required.
Because the most frequent causes of axle differen-
t i a l noise are incorrect r i n g gear backlash and/or dif-
ferential bearing preload torque. A few routine
adjustments could be a l l t h a t is necessary to correct
the problem. Therefore, before axle differential disas-
sembly, the following measurements should be made:
• R i n g gear backlash.
• Drive pinion gear shaft preload torque.
Record and analyze the results. These measure-
ments w i l l aid i n determining the extent of the
required axle differential service.
S E R V I C E P R O C E D U R E S
DIFFERENTIAL DRAIN AND REFILL
The lubricant recommended for this differential is
Mopar H i g h Performance Synthetic Axle Lube SAE
75 W / 1 4 0 (MS-8985). A container of Mopar Gear