Chrysler RAM TRUCK 2500 1994 Service Manual page 76

• FRONT SUSPENSION AND AXLE 2 - 19
A X L E NOISE/VIBRATION DIAGNOSIS
INDEX
page page
. . 20
. . 19
General Information 19
Orivellne Snap 20 Low Speed Knock 20
Gear and Bearing Noise 19 Vibration 20
GENERAL INFORMATION
Axle bearing problem conditions are usually caused
by:
• Insufficient or incorrect lubricant
• Foreign matter/water contamination
• Incorrect bearing preload torque adjustment
• Incorrect backlash ( to tight)
When serviced, the bearings must be cleaned thor­
oughly. They should be dried with lint-free shop tow­
els. Never dry bearings with compressed air.
This will overheat them and brinell the bearing
surfaces. This will result i n noisy operation af­
ter repair.
Axle gear problem conditions are usually the result
of:
• Insufficient lubrication
• Incorrect or contaminated lubricant
• Overloading (excessive engine torque)
• Exceeding vehicle weight capacity
• Incorrect clearance or backlash adjustment
Insufficient lubrication is usually the result of a
housing cover leak. I t can also be from worn axle
shaft or pinion gear seals. Check for cracks or porous
areas i n the housing or tubes.
Using the wrong lubricant will cause overheating
and gear failure. Gear tooth cracking and bearing
spalling are indicators of this.
Axle component breakage is most often the result
of: -
© Severe overloading
• Insufficient lubricant
• Incorrect lubricant
• Improperly tightened components
Common causes of overloading is from full-throttle
acceleration. Overloading happens when towing
heavier-than-recommended loads. Compdnent break­
age can occur when the wheels are spun excessively.
Insufficient or incorrect lubricants contribute to
breakage through overheating. Loose differential
components can also cause breakage.
Incorrect bearing preload or gear backlash will not
result i n component breakage. This will cause accel­
erated wear and contribute to early failure. Mis-ad­
justment will produce noise. I f a mis-adjustment
condition is not corrected, component failure can re­
sult.
Excessive bearing preload may not be noisy. This
condition will cause high temperature which can re­
sult i n bearing failure.
GEAR AND BEARING NOISE
G E A R NOISE
Axle gear noise can be caused by insufficient lubri­
cant. Incorrect backlash, tooth contact, or worn/dam­
aged gears can cause noise.
Gear noise usually happens at a specific speed
range. The range is 30 to 40 mph, or above 50 mph.
The noise can also occur during a specific type of
driving condition. These conditions are acceleration,
deceleration, coast, or constant load.
When road testing, accelerate the vehicle to the
speed range where the noise is the greatest. Shift
out-of-gear and coast through the peak-noise range.
I f the noise stops or changes greatly, check for insuf­
ficient lubricant. Incorrect ring gear backlash, or
gear damage can cause noise changes.
Differential side and pinion gears can be checked
by turning the vehicle. They usually do not cause
noise i n straight-ahead driving. These gears are
loaded during vehicle turns. I f noise does occur dur­
ing vehicle turns, the side or pinion gears could be
worn or damaged. A worn pinion gear mate shaft can
also cause a snapping or a knocking noise.
BEARING NOISE
The axle shaft, differential and pinion gear bear­
ings can all produce noise when worn or damaged.
Bearing noise can be either a whining, or a growling
sound.
Pinion gear bearings have a constant-pitch noise.
This noise changes only with vehicle speed. Pinion
bearing noise will be higher because i t rotates at a
faster rate. Drive the vehicle and load the differen­
tial. I f bearing noise occurs the pinion rear bearing is
the source of the noise. I f the bearing noise is heard
during a coast, front bearing is the source.
Worn, damaged differential bearings usually pro­
duce a low pitch noise. Differential bearing noise is
similar to pinion bearing. The pitch of differential
bearing noise is also constant and varies only with
vehicle speed.