Driveline Vibration

Driveline vibration exhibits a higher frequency and lower amplitude than does high-speed shake. Driveline vibration is directly related to the speed of the vehicle and is usually noticed at speeds of 72 km/in (45 mph) or higher. Driveline vibration can be perceived as a tremor in the floorpan or is heard as a rumble, hum or boom. Driveline vibration can exist in all drive modes, but may exhibit different symptoms depending upon whether the vehicle is accelerating, decelerating, floating or coasting. If the vibration is particularly noticeable during acceleration or deceleration, especially at lower speeds, check the driveline angle. Driveline vibration can be duplicated by supporting the axle upon a hoist or upon jack stands, though the brakes may need to be applied lightly in order to simulate road resistance.

1. Raise the vehicle promptly after road testing, on a twin-post hoist or jack stands, to prevent tire flat-spotting. Engage the drivetrain and accelerate to the observed road test speed to verify the presence of the vibration. If it is not evident, check the non-driving wheels with a wheel-balancer to rule out imbalance as a possible cause. If required, balance the non-driving wheels and repeat the road test. If the vibration is still evident, proceed to Step 2.
2. If the vibration appeared during the road speed hoist test, mark the relative position of the drive wheels on the rear axle or wheel lugs to permit reinstallation in the original position, and remove the wheels. Secure the brake drums, if present, by installing all the lug nuts in the reversed position and repeat the road speed acceleration. If the vibration is gone, check the wheels and tires. If the vibration persists, proceed to Step 3.
3. Inspect the driveshaft for signs of physical damage, a missing balance weight, undercoating, or improperly seated, worn, or binding universal joints. Check the index marks (paint spots) on the rear of the driveshaft and rear axle companion flange. If these marks are more than 90 degrees apart, disconnect the driveshaft and reindex to align the marks as close as possible. Clean the driveshaft and replace the rear axle shaft universal joints as necessary, or replace the driveshaft if damaged. After any corrections are made, recheck the vibration at the road test speed. If the vibration is gone, reinstall the wheels and road test. If the vibration persists, proceed to Step 4.
4. With the vehicle on a hoist and the wheels off, measure the runout at the front, center, and rear of the driveshaft with the indicator, rotating the driveshaft by turning a brake drum or rotor. On a one-piece driveshaft, if the runout exceeds 0.89 mm (0.035 inch) at the front or center, the driveshaft must be replaced. If the front and center are within this limit, but the rear runout is not, mark the rear runout high point and proceed to Step 5. If the runout is within the limits at all points, proceed to Step 7.
5. Note or mark the indexing of the driveshaft to the rear axle companion flange. Disconnect the driveshaft, reindex 180 degrees, and reconnect. Circular rear axle companion flanges can be indexed in 45-degree increments to fine tune the runout condition; half-round rear axle companion flanges are limited to two positions. Check the runout at rear of the driveshaft, and if it is still over 0.89 mm (0.035 inch), mark the high point and proceed to Step 6. If the runout is no longer excessive, check for vibration at the road test speed, and, if still present, reindex the driveshaft slip yoke on the transmission output shaft 180. degrees and road test the vehicle. If the vibration persists, proceed to Step 7 or the driveshaft balancing procedure.

NOTE: Move the universal joints in each direction of rotation during reindexing. If a universal joint feels stiff or has a gritty feel in any direction, replace the universal joints.





6. Excessive driveshaft runout can originate in the driveshaft itself or in the rear axle companion flange. To determine which component is the concern, compare the two high points marked in Steps 4 and 5. If the marks are close together, within about 25 mm (1 inch), the shaft is eccentric, and should be checked for vibration. Replace as necessary.





If the marks are on opposite sides of the driveshaft, about 180 degrees apart, the yoke or rear axle companion flange is responsible. Replace as necessary.

After replacing, check for runout. When replacing a rear axle companion flange, the driveshaft runout must not exceed 0.89 mm (0.035 inch). When runout 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 driveshaft. Best positioning of the hose clamp head(s) can be determined by trial and error, if special balancing equipment is not available.





8. 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 driveshaft with its head at position No. 1.
9. Check for vibration at road speed. Recheck 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 the condition is still not acceptable, add a second clamp at the same position and recheck vibration.





11. If no improvement is noted, rotate the clamps in opposite directions, equal distances from the best position determined in Step 8. Initially, separate the clamp heads about 13 mm (1/2 inch), and recheck the vibration at the road speed.
12. Repeat the process with increasing separation until the best combination is found, or the vibration is reduced to an acceptable level.
13. Install the wheels and road test, since vibration noticeable on the hoist may not be evident during the road test. If the vibration is still not acceptable, replace the rear axle driveline vibration damper, if so equipped. If the road test is not acceptable, replace the ring gear and pinion.