Jeep Cherokee (XJ): Diagnosis and testing

Vibration

Tires that are out-of-round, or wheels that are unbalanced, will cause a low frequency vibration.

Refer to Group 22, Tires and Wheels, for additional information.

Brake drums that are unbalanced will cause a harsh, low frequency vibration. Refer to Group 5, Brakes, for additional information.

Driveline vibration can also result from loose or damaged engine mounts. Refer to Group 9, Engines, for additional information.

Propeller shaft vibration increases as the vehicle speed is increased. A vibration that occurs within a specific speed range is not usually caused by a propeller shaft being unbalanced. Defective universal joints, or an incorrect propeller shaft angle, are usually the cause of such a vibration.

DRIVELINE VIBRATION

Unbalance

NOTE: Removing and re-indexing the propeller shaft 180 relative to the yoke may eliminate some vibrations.

If propeller shaft is suspected of being unbalanced, it can be verified with the following procedure:

1.  Raise the vehicle.
2.  Clean all the foreign material from the propeller shaft and the universal joints.
3.  Inspect the propeller shaft for missing balance weights, broken welds, and bent areas. If the propeller shaft is bent, it must be replaced.
4.  Inspect the universal joints to ensure that they are not worn, are properly installed, and are correctly 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. 6).

Fig. 6 Clamp Screw At Position 1

1 - CLAMP
2 - SCREWDRIVER

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. 7) and repeat the test.

Fig. 7 Two Clamp Screws At The Same Position

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. 8).

Fig. 8 Clamp Screws Separated

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 indicator will contact the shaft.
2.  The dial indicator must be installed perpendicular 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.  If the propeller shaft runout is out of specification, remove the propeller shaft, index the shaft 180, and re-install the propeller shaft. Measure shaft runout again.
6.  If the propeller shaft runout is now within specifications, mark the shaft and yokes for proper orientation.
7.  If the propeller shaft runout is not within specifications, verify that the runout of the transmission/ transfer case and axle are within specifications. Correct as necessary and re-measure propeller shaft runout.
8.  Replace the propeller shaft if the runout still exceeds the limits.

RUNOUT SPECIFICATIONS