TRUCK SERVICE MANUAL
To compensate for the alternate increase and
all vibrations are caused by the propeller shaft
decrease in shaft length caused by rear axle suspension
assembly. The vehicle should be thoroughly road tested
deflection, a slip joint is incorporated within the drive line.
or supported on floor stands in an attempt to isolate the
The slip joint is splined to accept the shaft, and it is
Check for out-of-round tires, unevenly worn tires,
rotation of the slip joint.
tires and wheels out of balance, wheels and rims
out of alignment or mismatched tires.
A correctly phased propeller shaft is one in which the
2. Engine, Clutch, Transmission and Axle
yoke bores or flange ears are in the same plane, Fig. 5.
Check for engine misfire on one or more
Propeller shaft phasing affects joint cancellation in
cylinders, low compression, loose engine
that an incorrectly phased shaft will induce torsional
mounts, valves out of adjustment, loose
excitation (shaft windup and unwind).
flywheel, defective vibration damper, broken or
bent fan blades, excess bell housing run-out,
It can be see in Fig. 4 that a propeller shaft is out of
pressure plate out of balance, loose driven
phase any time that the slip joint yoke bore or flange ear
member hub, piece of lining broken from driven
center line is rotated to any point between 0 and 180
member, worn pilot bearings, worn or noisy
degrees with respect to the yoke or flange at the
transmission bearings, worn rear axle bearings,
opposite end of the shaft. Positioning the yoke at one
broken or chipped gear teeth, bent axle housing
end of the shaft at 0 degrees and the slip joint yoke at 90
or worn front axle suspension and linkage.
degrees results in a maximum out-of-phase condition
3. Frame and Springs
and torsional excitation will be greatest. Drive line
vibration will be severe.
Check for mismatched springs, broken or shifted
rear springs, broken spring seats, loose spring
To provide correct propeller shaft phasing, the slip
U-bolts or a bent, twisted or broken frame.
joint and shaft are marked with arrows or dots, Fig. 6. If
4. Propeller Shaft Assembly
these markings are not visible, mark shaft and slip joint
before disassembling joint. During reassembly align slip
Propeller shaft vibrations and remedies are
joint arrow with shaft arrow.
covered in detail herein.
UNIVERSAL JOINT AND PROPELLER SHAFT
Most propeller shaft troubles which cause drive line
vibration are the result of something affecting either drive
line balance or drive line alignment.
Vibration originating in the universal joint and
propeller shaft assembly is usually present only at certain
speeds and cycle as the shaft speed is raised and
Fig. 6. Slip Joint Alignment Arrows
lowered. This intermittent characteristic differs from the
generally constant noise set up throughout the vehicle's
The propeller shaft will still be in phase if the arrows
speed range by drive unit gears.
are 180 degrees apart; however, this is not standard
practice. In other words, the position of the slip joint
Propeller shaft vibration is a definite indication that a
arrow with respect to the shaft arrow cannot be at any
problem exists in the area of the shaft assembly. To
point except in line or 180 degrees from alignment.
prevent possible hazardous consequences and damage
to other components, the vehicle should not be operated
other than to isolate the trouble until the problem has
Vibration that is felt during vehicle operation will
generally fall in one or more of the following categories.
It can be readily seen that not