Drive Shaft RUNOUT

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 be perceived as a tremor in the floorpan or 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 appropriate 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 and 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 necessary, balance the non-driving wheels and repeat the road test. If the vibration is still evident, go to next step.
2. Mark the relative position of the wheel/tire assemblies to the lug nuts. Remove the rear wheel/tire assemblies. Install all the lug nuts in the reverse position (wheel nuts can be installed in their normal orientation on axles with dual rear wheels) and repeat the road speed acceleration. If the vibration is gone, inspect wheel/tire assemblies for proper runout. If the vibration persists, go to next step.
3. Inspect the drive shaft(s) for signs of physical damage, missing balance weights, undercoating, incorrect seating, wear and binding "U" joints. Clean the drive shaft and install NEW "U" joints or install a NEW drive shaft if damaged. Check the index marks (paint spots) on the rear of the drive shaft and axle pinion flange. If these marks are more than 1/4 turn apart, disconnect the drive shaft and re-index to align the marks as closely as possible. Check the alignment of the index marks on the drive shaft to transmission tail shaft. For E150 and E250 vehicles, if a yellow dot is visible on the front of the drive shaft, it can be aligned with a yellow dot on the transmission output shaft. After any corrections are made, recheck for vibration at the road test speed. If the vibration is gone, reinstall the rear wheel/tire assemblies and road test vehicle. See TORQUE SPECIFICATIONS . If the vibration persists, go to next step.
4. Raise the vehicle on a hoist and remove the wheels. Rotate the drive shaft by turning the axle and measure the runout at the front, the center, and the rear of the drive shaft with the indicator. If the runout exceeds 0.020" (0.50 mm) at the front or center, install a NEW drive shaft. If the front and center are within this limit, but the rear runout is not, mark the rear runout high point and go to next step. See Fig 1. If the runout is within the limits at all points, go to step  7.
NOTE: Check the "U" joints during re-indexing. If a "U" joint feels stiff or gritty, install NEW "U" joints.
5. Scribe alignment marks on the drive shaft and the pinion flange. Disconnect the drive shaft, rotate it one-half turn, and reconnect it. Circular pinion flanges can be turned in 1/4 increments to fine tune the runout condition. Half round pinion flanges are limited to 2 positions. Check the runout at the rear of the drive shaft. If it is still over 0.020" (0.50 mm), mark the high point and go to next step. If the runout is no longer excessive, check for vibration at the road test speed. If vibration is still present, re-index the drive shaft slip yoke on the transmission output shaft one-half turn and road test the vehicle. If the vibration persists, go to step  7.
6. Excessive drive shaft runout may originate in the drive shaft itself or in the pinion flange. To determine which, compare the 2 high points marked in Steps 4 and 5. If the marks are close together, within about 0.98" (25 mm), install a NEW drive shaft and road test the vehicle. See Fig 2. If the marks are on opposite sides of the drive shaft, the pinion flange is responsible for the vibration. When installing a NEW pinion flange, the drive shaft runout must not exceed 0.020" (0.50 mm). When runout is within limits, recheck for vibration at road speed. If vibration persists, balance the drive shaft.
7. To balance the drive shaft, install one or 2 hose clamps on the drive shaft, near the ends. Position of the hose clamp head(s) can be determined through trial and error.
8. Mark the rear of the drive shaft into 4 equal sectors, and number the marks 1-4. Install a hose clamp on the drive shaft with its head at position No. 1. See Fig 3. 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. See Fig 4. If no improvement is noted, rotate the clamps in opposite directions, equal distances from the best position. Separate the clamp heads about 0.51" (13 mm) and recheck for vibration at the road speed.
10. Repeat the process with increasing separation until the best combination is found or the vibration is reduced to an acceptable level. See Fig 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 drive shaft. If the vibration is still not acceptable, see appropriate DIFFERENTIALS & AXLE SHAFTS article for differential case and ring gear runout checks.

Fig 1: Marking High Point On Drive Shaft

Courtesy of FORD MOTOR CO.

Fig 2: Reading Drive Shaft Runout Marks

Courtesy of FORD MOTOR CO.

Fig 3: View Of Sector Marks On Drive Shaft

Courtesy of FORD MOTOR CO.

Fig 4: View Of Second Clamp

Courtesy of FORD MOTOR CO.

Fig 5: View Of Clamp Placement

Courtesy of FORD MOTOR CO.