Driveline Vibration
DRIVELINE VIBRATIONDriveline 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 speed ranges. 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. 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. 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 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 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, see the runout procedure in See WHEEL HUB BOLT CIRCLE RUNOUT. Wheel Hub Bolt Circle Runout If vibration persists, proceed to Step 3.
3. Inspect the propeller shaft(s) for signs of physical damage, missing balance weight, undercoating, improper seating, wear and binding universal joints. Clean the propeller shaft and replace the universal joints or replace the propeller shaft if damaged. Check the index marks (paint spots) on the rear of the propeller shaft and rear companion flange. If these marks are more than one-quarter turn apart, disconnect the propeller shaft 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 vibration is gone, reinstall the wheels and road test. If vibration persists, proceed to Step 4.
4. Raise the vehicle on a hoist and remove the wheels. Rotate the propeller shaft by turning the axle and measure the runout at the front, the center, and the rear of the propeller shaft with the indicator. If runout exceeds 0.89 mm (0.035 inch) at the front or center, the propeller shaft 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.
Note:
- Check the universal joints during re-indexing. If a universal joint feels stiff or gritty, replace the universal joints.
5. Scribe alignment marks on the propeller shaft and the rear companion flange. Disconnect the propeller shaft, rotate it one-half turn, and reconnect it. Circular companion flanges can be turned in one-quarter increments to fine tune the runout condition; half-round companion flanges are limited to two positions. Check the runout at the rear of the propeller shaft. If it is still over 0.89 mm (0.035 inch), mark the high point and proceed to Step 6. If runout is no longer excessive, check for vibration at the road test speed. If vibration is still present, re-index the propeller shaft slip yoke on the transmission output shaft one-half turn and road test the vehicle. If vibration persists, proceed to Step 7.
6. Excessive propeller shaft runout may originate in the propeller shaft itself or in the axle companion flange. 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 replaced and the vehicle road tested.
If the marks are on opposite sides of the propeller shaft, the yoke or rear companion flange is responsible for the vibration.
When replacing a rear companion flange, the propeller shaft 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 propeller shaft.
7. To balance the propeller shaft, install one or two hose clamps on the propeller shaft, near the rear. Position of the hose clamp head(s) can be determined by trial-and-error.
8. Mark the rear of the propeller shaft into four approximately equal sectors and number the marks 1 through 4. Install a hose clamp on the propeller shaft 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, replace the axle drive line vibration damper first, if so equipped. If the vibration is still not acceptable, see DIFFERENTIAL CASE AND RING GEAR REAR (STANDARD) DISASSEMBLY / ASSEMBLY or See DIFFERENTIAL CASE AND RING GEAR REAR (LIMITED SLIP) DISASSEMBLY / ASSEMBLY.