Dodge 2000 DURANGO Service Manual page 118

3 - 68 8 1/4 AND 9 1/4 AXLE
DIAGNOSIS AND TESTING (Continued)
When road testing, first warm-up the axle fluid by
driving the vehicle at least 5 miles and then acceler-
ate the vehicle to the speed range where the noise is
the greatest. Shift out-of-gear and coast through the
peak–noise range. If the noise stops or changes
greatly:
• Check for insufficient lubricant.
• Incorrect ring gear backlash.
• Gear damage.
Differential side gears and pinions can be checked
by turning the vehicle. They usually do not cause
noise during straight–ahead driving when the gears
are unloaded. The side gears are loaded during vehi-
cle turns. A worn pinion mate shaft can also cause a
snapping or a knocking noise.
BEARING NOISE
The axle shaft, differential and pinion bearings can
all produce noise when worn or damaged. Bearing
noise can be either a whining, or a growling sound.
Pinion bearings have a constant–pitch noise. This
noise changes only with vehicle speed. Pinion bearing
noise will be higher pitched because it rotates at a
faster rate. Drive the vehicle and load the differen-
tial. If bearing noise occurs, the rear pinion bearing
is the source of the noise. If the bearing noise is
heard during a coast, the front pinion bearing is the
source.
Worn or damaged differential bearings usually pro-
duce a low pitch noise. Differential bearing noise is
similar to pinion bearing noise. The pitch of differen-
tial bearing noise is also constant and varies only
with vehicle speed.
Axle shaft bearings produce noise and vibration
when worn or damaged. The noise generally changes
when the bearings are loaded. Road test the vehicle.
Turn the vehicle sharply to the left and to the right.
This will load the bearings and change the noise
level. Where axle bearing damage is slight, the noise
is usually not noticeable at speeds above 30 mph.
LOW SPEED KNOCK
Low speed knock is generally caused by a worn
U–joint or by worn side–gear thrust washers. A worn
pinion shaft bore will also cause low speed knock.
VIBRATION
Vibration at the rear of the vehicle is usually
caused by a:
• Damaged drive shaft.
• Missing drive shaft balance weight(s).
• Worn or out–of–balance wheels.
• Loose wheel lug nuts.
• Worn U–joint(s).
• Loose/broken springs.
• Damaged axle shaft bearing(s).
• Loose pinion nut.
• Excessive companion flange run out.
• Bent axle shaft(s).
Check for loose or damaged front–end components
or engine/transmission mounts. These components
can contribute to what appears to be a rear–end
vibration. Do not overlook engine accessories, brack-
ets and drive belts.
All driveline components should be examined
before starting any repair.
Refer to Group 22, Wheels and Tires, for additional
vibration information.
DRIVELINE SNAP
A snap or clunk noise when the vehicle is shifted
into gear (or the clutch engaged), can be caused by:
• High engine idle speed.
• Transmission shift operation.
• Loose engine/transmission/transfer case mounts.
• Worn U–joints.
• Loose spring mounts.
• Loose pinion nut and companion flange.
• Excessive ring gear backlash.
• Excessive side gear to case clearance.
The source of a snap or a clunk noise can be deter-
mined with the assistance of a helper. Raise the vehi-
cle on a hoist with the wheels free to rotate. Instruct
the helper to shift the transmission into gear. Listen
for the noise, a mechanics stethoscope is helpful in
isolating the source of a noise.
TRAC–LOK DIFFERENTIAL NOISE
The most common problem is a chatter noise when
turning corners. Before removing a Trac-lok
for repair, drain, flush and refill the axle with the
specified lubricant. Refer to Lubricant change in this
Group.
A container of Mopar
tion modifier) should be added after repair service or
during a lubricant change.
After changing the lubricant, drive the vehicle and
make 10 to 12 slow, figure-eight turns. This maneu-
ver will pump lubricant through the clutches. This
will correct the condition in most instances. If the
chatter persists, clutch damage could have occurred.
TRAC–LOK TEST
WARNING: WHEN SERVICING VEHICLES WITH A
TRAC–LOK DIFFERENTIAL DO NOT USE THE
ENGINE TO TURN THE AXLE AND WHEELS. BOTH
REAR WHEELS MUST BE RAISED AND THE VEHI-
CLE SUPPORTED. A TRAC–LOK
EXERT ENOUGH FORCE IF ONE WHEEL IS IN CON-
TACT WITH A SURFACE TO CAUSE THE VEHICLE
TO MOVE.
Trac-lok Lubricant (fric-
AXLE CAN
DN
unit