Chevrolet Light Duty Truck 1973 Service Manual page 239

COMPLAINT
Roughness, Vibration or
Body Boom at any speed.
NOTE: With tachometer
installed in car, determine
whether propeller 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 (rpm)
at which vibration was
noted before. Note the
effect on the vibration.
If vibration occurs at the
same engine speed (rpm),
regardless of transmission
gear range selected, drive
shaft assembly is not at
fault, since the shaft
speed (rpm) varies.
If vibration decreased, or
is eliminated, in a
different gear range but
at the same engine speed
(rpm), check the
possible causes:
Roughness usually at low speeds,
light load, 15-35 mph.
Scraping noise.
Roughness on heavy
acceleration (short duration.)
Roughness -- above 35 mph
felt and/or heard.
POSSIBLE CAUSE
a. Bent or dented drive shaft.
b. Undercoating on drive shaft.
c. Tire unbalance. (30-80 mph, not
throttle conscious)
d. Excessive U-bolt torque.
e. Tight universal joints.
f. Worn universal joints.
g. Burrs or gouges on
companion flange. Check
snap ring locating surfaces
on flange yoke.
h. Drive shaft or companion
flange unbalance.
i. Excessive looseness at slip
yoke spline.
j. Drive shaft runout (50-80 mph
throttle conscious)
a. U-bolt clamp nuts excessively
tight.
a. Slinger, companion flange, or
end yoke rubbing on rear axle
carrier.
a. Double cardan joint ball seats
worn. Ball seat spring may be
broken.
a. Tires unbalanced or worn.
Fig. 33B—Diagnosis Chart B
REAR S U S P E N S IO N A N D DRIVELINE
CORRECTION
a. Replace.
b. Clean drive shaft.
c. Balance or replace as required.
d. Check and correct to specified torque.
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. Rework or replace companion flange.
h. Check for missing balance weights
on drive shaft. Remove and
reassemble drive shaft to companion
flange, 180° from original position.
i. Replace necessary parts.
j. Check drive shaft runout at front and
rear. Should be less than specified. If
above, rotate shaft 180° and recheck.
If still above specified, replace shaft.
a. Check and correct torque to that
specified. If torque was excessive
or if brenelled pattern on trunnions
is evident, replace joints.
a. Straighten slinger to remove
interference.
a. Replace joint and shaft assembly.
a. Balance or replace as required.
LIGHT DUTY TRUCK SERVICE MANUAL
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