Pontiac FIREBIRD 1972 Service Manual page 328

4A-4 1972 PONTIAC SERVICE MANUAL
Drive-Line Squeal and Squeak
Propeller Shaft Vibration
Oil Leaks
PRE-REPAIR INVESTIGATION
A close examination of the differential prior to disassem-
bly will often reveal valuable information as to the extent
and type of repairs or adjustments necessary. The infor-
mation gained, with the report of malfunctioning, will
provide a basis for determining the degree of disassembly
required. Since the frequent causes of axle noise are im-
proper backlash or side bearing preload, or both, a few
simple adjustments may be all that is necessary to correct
a problem.
between side gear hub and counterbore in case,
worn thrust washers and excessive drive pinion
and ring gear backlash. Remove worn parts and
replace as required, selecting close fitting
parts when possible. Adjust pinion and ring
gear backlash.
Squeals and squeaks are audible at low
speeds, seldom over 20 mph. A continuous
squeal is from the pinion oil seal. Seal
squeaks frequently correct themselves; a
persistent squealing seal should be replaced.
Objectional vibrations at high speed (65 mph
or higher) may be caused by a propeller shaft
that is out of balance. Out of balance may be
due to a bent shaft.
To determine whether propeller shaft is causing
vibration, drive car through speed range and
note speed at which vibration is most pronounced.
Shift transmission into lower gear range and
drive car at same engine speed as when vibration
was most pronounced in direct drive. Note
effect on vibration.
To determine engine speed, divide vehicle speed
by the lower transmission gear ratio used
(can be found at end of appropriate chapter
in shop manual).
If the vibration is still present at the same
engine speed, whether in direct drive or in
the lower gear, since the propeller shaft
speed varies, this cannot be the fault. If
the vibration decreases or is eliminated in
the lower gear, then the propeller shaft is
out of balance and should be rebalanced or
replaced.
See propeller shaft Section 4E for further
trouble diagnosis.
It is difficult to determine the source of
some oil leaks. Even after the point of
leakage has been determined, it is hard to
tell whether the oil is leaking past the
lip of the seal or past the O.D. of the seal.
Therefore, it is a good idea to make sure
the leak is stopped by using a nonhardening
sealing compound around the O.D. of the new
seal.
Therefore, before removing the differential from the hous-
ing, the following checks should be made, with the results
recorded and analyzed:
A.
sicklash
B. Pinion Bearing Preload
C. Red Lead Test
Use care at all times to keep dirt and other foreign mat-
ter, such as grinder dust, soot or sand away from