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4A-2
1977 PONTIAC SERVICE M A N U A L
DIAGNOSIS
PROPELLER SHAFT TROUBLE
DIAGNOSIS
Condition
Possible Cause
Correction
Leak at front slip
yoke. (An occasional
drop of lubricant
leaking from splined
yoke is normal and
requires no attention.)
Knock in drive line
clunking noise when
car is operated under
float condition at 10
mph in high gear or
"Neutral".
Ping, snap or click
in drive line.
Scraping noise.
1. Rough outside surface
on slip yoke.
2. Defective trans-
mission rear oil seal.
1. Worn or damaged
universal joints.
2. Side gear hub
counterbore in
differential worn
.oversize.
1. Loose upper or
lower control arm
bushing bolts.
2. Worn or damaged
Universal joints.
Slinger, pinion
flange, or end yoke
rubbing on rear axle
carrier.
1. Replace seal if cut by burrs
on yoke. Minor burrs can be
smoothed by careful use of
crocus cloth or honing with
a fine stone. Replace yoke
if outside surface is rough
or burred badly.
2. Replace transmission rear
oil seal.
Bring transmission oil
up to proper level after
correction.
1. Replace
2. Replace differential
case and/or side gears
as required.
1. Tighten bolts to
specified torque.
2. Replace.
Straighten slinger
to remove interference.
Objectional vibration, roughness, rumble or boom can
If the problem is still present at the same engine speed
be caused by the input from a number of systems. The chart
whether in direct drive or in the lower gear range, since the
(Fig. 4A-2) provides a systematic approach to finding the
propeller shaft speed varies, it cannot be at fault. If problem
vehicle problem.
decreases or is eliminated in a different gear range but at the
same engine speed, check the possible causes in Fig. 4A-2.
To determine whether the propeller shaft is causing the
problem, drive vehicle through speed range and note speed
(vehicle and/or engine) at which problem is most pronounced
(tachometer may be used). Shift transmission into a lower
gear range and drive vehicle at same engine speed as when
problem was most pronounced in direct drive. Note effect on
problem.
To determine engine speed, if tachometer is not used,
divide vehicle speed by the transmission gear ratio in which
the problem occurs.
Example: With the T H M 350 in Low range, divide by
1.52. If problem is not pronounced in direct drive at 55 mph,
the same engine speed would be produced in in Low
range(THM 350) at 55/1.52
"
36 mph.
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