Jeep 1997 Grand Cherokee Service Manual page 63

ZG
DIAGNOSIS AND TESTING (Continued)
(3) Inspect the propeller shaft for missing balance
weights, broken welds, and bent areas. If the pro-
peller shaft is bent, it must be replaced.
(4) Inspect the universal joints to ensure that they
are not worn, are properly installed, and are cor-
rectly aligned with the shaft.
(5) Check the universal joint clamp screws torque.
(6) Remove the wheels and tires. Install the wheel
lug nuts to retain the brake drums or rotors.
(7) Mark and number the shaft six inches from the
yoke end at four positions 90° apart.
(8) Run and accelerate the vehicle until vibration
occurs. Note the intensity and speed the vibration
occurred. Stop the engine.
(9) Install a screw clamp at position 1 (Fig. 7).
Fig. 7 Clamp Screw At Position 1
(10) Start the engine and re-check for vibration. If
there is little or no change in vibration, move the
clamp to one of the other three positions. Repeat the
vibration test.
(11) If there is no difference in vibration at the
other positions, the source of the vibration may not
be propeller shaft.
(12) If the vibration decreased, install a second
clamp (Fig. 8) and repeat the test.
(13) If the additional clamp causes an additional
vibration, separate the clamps (1/4 inch above and
below the mark). Repeat the vibration test (Fig. 9).
(14) Increase distance between the clamp screws
and repeat the test until the amount of vibration is
at the lowest level. Bend the slack end of the clamps
so the screws will not loosen.
(15) If the vibration remains unacceptable, apply
the same steps to the front end of the propeller shaft.
(16) Install the wheel and tires. Lower the vehicle.
RUNOUT
(1) Remove dirt, rust, paint, and undercoating
from the propeller shaft surface where the dial indi-
cator will contact the shaft.
CLAMP SCREWDRIVER
DIFFERENTIAL AND DRIVELINE
Fig. 8 Two Clamp Screws At The Same Position
Fig. 9 Clamp Screws Separated
(2) The dial indicator must be installed perpendic-
ular to the shaft surface.
(3) Measure runout at the center and ends of the
shaft sufficiently far away from weld areas to ensure
that the effects of the weld process will not enter into
the measurements.
(4) Refer to Runout Specifications chart.
(5) Replace the propeller shaft if the runout
exceeds the limit.
RUNOUT SPECIFICATIONS
Front of shaft
Center of shaft
Rear of shaft
NOTE: Measure front/rear runout approximately 3
inches (76 mm) from the weld seam at each end of
the shaft tube for tube lengths over 30 inches. Under
30 inches the max. runout is 0.20 inch for full length
of the tube.
1 ⁄ INCH
2
3 - 5
0.010 in. (0.25 mm)
0.015 in. (0.38 mm)
0.010 in. (0.25 mm)