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46-8
1977 PONTIAC SERVICE MANUAL
BODY BOOM NOISE OR VIBRATION
Objectional "body boom" noise or vibration can be
caused by an unbalanced propeller shaft. Excessive looseness
at the spline can contribute to this unbalance.
Other items that may also contribute to the noise
problem are as follows:
1 . Undercoating or mud on the shaft, causing unbalance.
2. Shaft or pinion flange balance weights missing.
3. Shaft damage, such as bending, dents or nicks.
4. Tire-type roughness. Switch tires from a known good
car to determine tire fault.
OIL LEAKS
It is difficult to determine the source of some oil leaks.
When there is evidence of an oil leak, determine source as
follows:
1 . Oil coming from the axle housing at the brake backing
plate is caused by a leaking axle shaft seal.
ON CAR
POSITIVE TRACTION FLUSHING
PROCEDURE
The following procedure is established for flushing the
Positive Traction Differential in the event the wrong
lubricant is accidentally added:
1 . Drain original lubricant from differential housing.
2. Fill axle with a light, non-detergent engine oil.
3. Raise both rear wheels off floor.
4. With car properly supported, run car in "Drive" range
for three to four minutes. Do not exceed 30 mph on
speedometer or accelerate or decelerate rapidly.
5. Remove oil from axle.
6.
Repeat Steps 2, 3, 4 and 5. It is important that the
axle be flushed two times to ensure complete removal of the
original lubricant.
7. Fill differential housing with positive traction
lubricant, GM Part No. 1052271, or equivalent.
CORRECTING REAR AXLE
COMPANION FLANGE SPLINE LEAKS
Check and confirm that it is not a pinion seal I.D. or
O.D. leak, but a leak around the companion flange washer
or nut:
1 . Mark propshaft and companion flange to permit
proper alignment at reinstallation. Disconnect propshaft
from companion flange and support shaft out of the way. If
U-joint bearing cups are not held by a retainer strap, use a
piece of wire or tape to retain bearing cups in place.
2. Oil coming from between the pinion flange or the
pinion flange slinger and the carrier is caused by a leaking
pinion seal.
3. Oil leaking at the junction of the axle tubes to the
carrier, or at the puddle weld holes are difficult to repair.
Under no circumstances should any welding be done in
attempts to stop leaks in these areas. If the leak is severe, the
complete rear axle housing should be replaced.
TESTING POSITIVE TRACTION
DIFFERENTIAL
If there is a doubt that a Pontiac is equipped with a
Positive Traction Differential, or to determine if this option
is performing satisfactorily, a simple test can be performed:
1.
Place transmission in neutral.
2. Raise one wheel off floor and place a block of wood
in front and rear of opposite wheel.
3. Remove wheel cover and install torque wrench with
extension on lug nut.
4. Disregard breakaway torque and observe only torque
required to continuously turn wheel smoothly. If differential
assembly is equipped with Positive Traction Differential, the
rotating torque will be at least 35 Ib. ft.
SERVICE
2. Mark the position of the companion flange,
companion shaft, and nut so the proper companion bearing
pre-load can be maintained.
3. Remove companion flange nut and washer.
4. Clean cavity under companion flange washer with
lacquer thinner or equivalent (Fig. 4B-8).
COMPANION
J
4853
Fig.
48-8 Area
to be Filled with Silastic
5. Fill cavity over full with Group 8.800, Part No.
1051042 (Silastic 732 R.T.V.) or equivalent so that when the
washer is reinstalled, the sealer will ooze out around the
washer.
6.
Install companion flange nut and tighten to the same
position as marked in Step 2. While holding companion
flange, tighten nut
1/16"
beyond alignment marks.
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