Driveline Vibration

This is a higher-frequency, lower-amplitude vibration than high-speed shake, directly related to road speed, and usually more noticeable at higher road speeds, 72 km/h (45 mph) and up. It is felt in the floor pan or heard as a rumble, hum or boom. It will exist in all drive modes, but may vary somewhat in acceleration, deceleration, float or coast modes. If the vibration is particularly responsive to heavy acceleration or deceleration, especially at lower speeds, driveline angles should be checked. A driveline vibration can usually be duplicated with the axle supported on a hoist or jack stands; through light brake application while accelerating and decelerating, to simulate road load resistance, may be necessary to bring it out.

1. Raise vehicle promptly after road-testing, on twin post hoist or jack stands, to prevent tire flat- spotting. Engage drive train and run-up to observed road test speed to verify presence of vibration. If not evident, check non-driving wheels with wheel-balancer spinner to rule out imbalance as a possible cause. On 4x4's, unlock front hubs or remove hub covers before spinning wheels. If required, balance non- driving wheels and repeat road test. If vibration is still evident, proceed to driveshaft inspection, Step 3.

2. If vibration appeared in road-speed hoist-test, mark relative position of drive wheels on axle or hub lugs to permit re-installation in original position, and remove wheels. Secure brake drums, if present, by installing all lug nuts in reversed position, and repeat road-speed run-up. If vibration is gone, check drive wheel run-out and balance. If vibration persists, proceed to Step 3.




3. Inspect driveshaft for signs of physical damage, missing balance weight, undercoating, or improperly seated, worn, or binding universal joints. Check the index marks (paint spots) on rear of shaft and pinion yoke or companion flange. If these marks are more than 90° apart, disconnect shaft and re-index to align marks as close as possible. Clean shaft and repair or replace universal joints as necessary, or replace shaft if damaged. After any corrections are made, re-check vibration at road test speed. If gone, re-install wheels and road test. If vibration persists, proceed to run-out check, Step 4.




4. With vehicle on hoist and wheels off, measure runout at front, center, and rear of driveshaft with indicator, rotating shaft by turning a brake drum or rotor. On a one-piece shaft, if run-out exceeds 0.89mm (0.035 inch) at front or center, the driveshaft must be replaced. If front and center are within this limit, but rear run-out is not, mark the rear run-out high point and proceed to Step 5. If run-out is within limits at all points, proceed to driveshaft balancing, Step 7.




5. Note or mark the indexing of driveshaft to rear axle pinion flange. Disconnect the shaft, re-index 180°, and re-connect. Check run-out at shaft rear, and if still over 0.89mm (0.035 inch), mark high point and see Step 6. If run-out is no longer excessive, check for vibration at road test speed, and, if still present, proceed to Step 7, driveshaft balancing under Adjustments.




6. Excessive driveshaft run-out may originate in the shaft itself or in the companion flange. To determine which, compare the two high points marked in Steps 4 and 5. If the marks are close together, within about 25mm or 1 inch, the shaft is eccentric, and should be replaced and checked for vibration. If the marks are on opposite sides of the shaft, about 180° apart, the yoke or flange is responsible. After replacing check for run-out. When replacing a yoke-type flange, driveshaft runout should not exceed 0.89mm (0.035 inch). When run-out is within limits, recheck for vibration at road speed. If vibration persists, balance the driveshaft.

7. Driveshaft balancing involves installing one or two hose clamps on the driveshaft, near the rear end of a one-piece shaft. Best positioning of the hose clamp head(s) can be determined by trial-and-error, if special balancing equipment is not available. If transducer-and- strobe equipment is available, see Adjustments in this Section for balancing procedure.

8. If the driveshaft was not previously indexed to correct run-out, mark original position of shaft relative to companion flange, index 180°, and road test. If after roadtest, the condition is not improved, return the shaft to the original position.




9. Mark off the rear of the driveshaft into four approximately equal sectors, and number the marks 1 through 4. Install a hose clamp on the shaft with its head at position No.1. Check for vibration at road speed. Re-check with the clamp at each of the other positions, to find the position for minimum vibration. If two adjacent positions show equal improvement, position the clamp head between them.








10. If condition is still not acceptable, add a second clamp at the same position and re-check vibration. If no improvement is noted, rotate the clamps in opposite directions, equal distances from the best position determined in Step 9. Initially, separate the clamp heads about 12mm or 1/2 inch, and re-check vibration at road speed.

Repeat the process with increasing separation until the best combination is found, or vibration is reduced to an acceptable level.

11. Install wheels and road test, since vibration noticeable on the hoist may not be evident during the road test. If vibration is still not acceptable, replace the axle pinion nose damper. If road test is not acceptable, replace axle ring gear and pinion set.