Driveline Vibration
Driveline VibrationNOTE: An analysis of vibration can also be conducted using the Vibration Analyzer and 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 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 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 nuts. Remove the wheels. Install all the wheel nuts in the reversed position and repeat the road speed acceleration. If the vibration is gone, refer to the tire and wheel runout procedure. If the vibration persists, proceed to Step 3. Component Tests and General Diagnostics
3. Inspect the driveshaft(s) for signs of physical damage, missing balance weight, undercoating, incorrect seating, wear and binding universal joints. Clean the driveshaft and install new universal joints or install a new driveshaft if damaged. Check the index marks (paint spots) on the rear of the driveshaft and axle pinion flange. If these marks are more than 1/4 turn apart, disconnect the driveshaft and reindex to align the marks as closely as possible. Check the alignment of the index marks on the driveshaft-to-transmission tailshaft. For E-150 and E-250 vehicles, if a yellow dot is visible on the front of the driveshaft, it can be aligned with a yellow dot on the transmission output shaft.
After any corrections are made, recheck for vibration at the speed where the symptom occurred. 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 driveshaft by turning the axle and measure the runout at the front, the center, and the rear of the driveshaft with the indicator. If the runout exceeds 0.89 mm (0.035 inch) at the front or center, the driveshaft must be installed new. 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: Check the U-joints during reindexing. If a U-joint feels stiff or gritty, install new U-joints.
Scribe alignment marks on the driveshaft and the axle pinion flange. Disconnect the driveshaft, rotate it 1/2 turn, and reconnect it. Circular axle pinion flanges can be turned in 1/4 increments to fine tune the runout condition; half-round axle pinion flanges are limited to 2 positions.
Check the runout at the rear of the driveshaft. 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 vibration is still present, reindex the driveshaft slip yoke on the transmission output shaft 1/2 turn and road test the vehicle. If the vibration persists, proceed to Step 7.
6. Excessive driveshaft runout may originate in the driveshaft itself or in the axle pinion flange. To determine which, compare the 2 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 yoke or axle pinion flange is responsible for the vibration.
When replacing an axle pinion 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. To balance the driveshaft, install 1 or 2 hose clamps on the driveshaft, near the rear. Position of the hose clamp head(s) can be determined by trial-and-error.
8. Mark the rear of the driveshaft into 4 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 2 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 axle driveline vibration damper first, if so equipped. If the vibration is still not acceptable, perform differential case and ring gear runout checks.