Driveline Vibration

Note: An analysis of driveline vibration can also be conducted using the Vibration Analyzer; following the manufacturer's directions.

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 various speeds. Driveline vibration can he 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. Check the driveline angles if the vibration is particularly noticeable during acceleration or deceleration, especially at lower speeds. 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. Note: When carrying out the following procedure steps on four-wheel drive vehicles, raise and support the vehicle so that all four wheels do not touch the ground.

Raise the vehicle promptly after road testing. Use 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 the vibration 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. Mark the relative position of the drive wheels to the wheel lugs. Remove the wheels. Install all the lug nuts in the reversed position and repeat the road speed acceleration. If the vibration is gone, refer to the tire and wheel runout. If the vibration persists, proceed to Step 3.
3. Inspect the driveshaft(s) for signs of physical damage, missing balance weight, undercoating, incorrect seating, wear and binding universal joints. Check the index marks (paint spots) on the rear of the driveshaft and axle pinion flange. If these marks are more than 90 degrees apart, disconnect the driveshaft and re-index to align the marks as closely as possible. After any corrections are made, recheck for 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. Raise the vehicle on a hoist and remove the wheels. Rotate the driveshafts by turning the axle and measure the runout at the front, the center, and the rear of the driveshafts with the indicator. If the runout exceeds 0.89 mm (0.035 inch) at the center, the driveshaft must be installed new. If the center is within limit, but the front or rear runout is not, mark the runout high points and proceed to Step 5. If the runout is within the limits at all points, proceed to Step 7.
5. Scribe alignment marks on the driveshaft and the pinion flanges. Disconnect the driveshaft, rotate it one-half turn, and reconnect it. Circular axle pinion flanges can be turned in one-quarter increments to fine tune the runout condition; half-round axle pinion flanges are limited to two positions. Recheck the runout. 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. If the vibration persists, proceed to Step 7.





6. Excessive driveshaft runout may originate in the driveshaft itself or in the pinion flanges. To determine which, 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 must be installed new and the vehicle road tested.





If the marks are on opposite sides of the driveshaft, the pinion flange is responsible for the vibration.
When installing or adjusting a pinion flange, the driveshaft runout must not exceed 0.064 mm (0.025 inch). When runout is within limits, recheck for vibration at road speed. If vibration persists, balance the driveshaft.
7. To balance the driveshaft, install one or two hose clamps on the driveshaft, near the ends. Position of the hose clamp head(s) can be determined by trial-and-error.





8. Mark 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.
Check for vibration at road speed. Recheck with the clamp at each of the other positions to find the position that shows minimum vibration. If two adjacent positions show equal improvement, position the clamp head between them.





9. If the vibration persists, add a second clamp at the same position and recheck for vibration.





If no improvement is noted, rotate the clamps in opposite directions, equal distances from the best position determined in Step 8. Separate the clamp heads about 13 mm (1/2 inch) and recheck for vibration at the road speed.
Repeat the process with increasing separation until the best combination is found or the vibration is reduced to an acceptable level.
10. Install the wheels and road test (vibration noticeable on the hoist may not be evident during the road test). If the vibration is still not acceptable, install a new driveshaft. If the vibration is still not acceptable, refer to differential case and ring gear runout checks.