Driveshaft Runout and Balancing
Driveshaft Runout and Balancing1. 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° 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 2.
2. 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 driveshafts with the indicator. If the runout exceeds specifications at the center, a new driveshaft must be installed. If the center is within limits, but the front or rear runout is not, mark the rear runout high points and proceed to Step 3. If the runout is within the limits at all points, proceed to Step 5.
3. 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. Recheck the runout. If it is still over specifications, mark the high point and proceed to Step 4. If the runout is no longer excessive, check for vibration at the road test speed. If vibration still persists, proceed to Step 5.
4. Excessive driveshaft runout may originate in the driveshaft itself or in the pinion flanges. To determine which, compare the 2 high points marked in Steps 2 and 3. If the marks are close together, within about 25 mm (1 inch), a new shaft must be installed 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 specifications. When runout is within limits, recheck for vibration at road speed. If vibration persists, balance the driveshaft.
5. 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.
5. To balance the driveshaft, install 1 or 2 hose clamps on the driveshaft, near ends. Position of the hose clamp head(s) can be determined by trial-and-error.
6. 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.
7. 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 (0.50 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.
8. 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.