Pontiac FIREBIRD 1972 Service Manual page 394

4E-2 1972 PONTIAC SERVICE MANUAL
4
CAUSE CORRECTION
a. Worn or damaged universal joints. a. Disassemble universal joints, inspect and
replace worn or damaged parts.
b. Side gear hub counterbore in differential worn b. Replace differential case and/or side gears
oversize. as required.
PING, SNAP OR CLICK IN DRIVE LINE
(Usually occurs on initial load application after transmis-
sion has been put in gear, either forward or reverse.)
CAUSE
a. Loose upper or lower control arm bushing
bolts.
b. Loose companion flange.
ROUGHNESS OR VIBRATION
With tachometer installed in car, determine whether pro-
peller shaft is cause of complaint by driving through speed
range and note the engine speed (rpm) at which vibration
(roughness) is most pronounced. Then, shift transmission
to a different gear range and drive car at same engine
speed (rprn) at which vibration was noted before. Note the
effect on the vibration:
CAUSE
a. Bent or dented propeller shaft.
b. Undercoating on propeller shaft.
c. Tire unbalance.
d. Excessive U-bolt torque.
e. Tight universal joints.
f. Worn universal joints.
g. U-joint retainer bent against bearing cup.
h. Burrs or gouges on companion flange.
i. Propeller shaft or companion flange unbalance.
CORRECTION
a. Tighten.
b. Remove companion flange, turn 180" from its
original position, apply white lead to splines and
reinstall. Pinion nut must be tightened to original
position.
If vibration occurs at the same engine speed (rpm), regard-
less of transmission gear range selected, propeller shaft
assembly is not at fault.
If vibration decreased, or is eliminated, in a different gear
range but at the same engine speed (rpm), check the fol-
lowing possible causes:
CORRECTION
a. Replace.
b. Clean propeller shaft.
c. Balance wheel and tire assemblies or replace
from a known good car.
d. Check and correct.
e. Impact yokes with a hammer to free up. Overhaul
joint if unable to free up or if joint feels rough when
rotated by hand.
f. Overhaul, replacing necessary parts.
g. Overhaul, replacing necessary parts.
h. Rework or replace companion flange.
i. Check fo'r missing balance weights on propeller
shaft. Remove and reassemble propeller shaft to
companion flange, 180" from original position.
j. Incorrect rear joint angle.
j. Check and correct trim height at curb weight.