Driveline Vibration
Driveline VibrationNOTE: 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 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 axle on a hoist or jack stands, though the brakes may need to be applied lightly to simulate road resistance.
1. After reviewing the customer complaint operate the vehicle and verify the condition. Do not make adjustments before carrying out a road test and a thorough visual inspection of the vehicle. Write down anything that does not look right. Do not change the tire pressure or the vehicle load. This may reduce the intensity of the condition to a point at which it cannot be identified clearly. Road test the vehicle and define the condition by reproducing it several times during the road test. During the road test:
^ A tachometer must be used.
^ Note the fuel level.
^ Note the vehicle speed, engine rpm and transmission gear used when the concern is present.
^ Find the speed at which the concern is most severe. Accelerate gently through this speed to 8 km/h (5 mph) above it. Then coast down 8 km/h (5 mph) below it. Note if the concern changes.
^ Drive the vehicle 8 km/h (5 mph) above the speed. Place the vehicle in NEUTRAL. Let the vehicle coast down. Note any changes.
^ Accelerate gently through this speed to 8 km/h (5 mph) above it. Disengage OVERDRIVE. It is important to evaluate rear axle vibration/noise concerns in DIRECT DRIVE rather than overdrive.
^ Maintain the speed at which the concern occurs. Note if the concern changes.
^ "Float" the driveline by easing off slightly on the accelerator at which the condition occurs. This is to unload the axle gears and universal joints.
2. Analyze the results of the road test. The concern should be directly related to vehicle road speed, not affected by acceleration or deceleration, or could not be reduced by coasting in NEUTRAL. The concern is independent of engine speed, and occurred at the same speed in any gear. If the concern does not change in all these modes of operation, the cause can be attributed to one of these typical causes of high speed vibrations:
^ Excessive tire/wheel imbalance
^ Excessive tire/wheel runout
^ Brake disc or drum imbalance
^ Driveshaft imbalance
^ Pinion flange runout or imbalance
^ Galled, dirty, rusty, incorrectly lubricated, damaged or worn slip yoke splines or U-Joints
^ Rear axle ring and pinion (gear pitch line runout)
3. NOTE: When carrying out the following procedure steps on 4-wheel drive vehicles, raise and support the vehicle so that all 4 wheels do not touch the ground.
Raise and support the vehicle on a twin post hoist immediately (to prevent tire flat-spotting) after the road test. Using a frame hoist will change driveline angles. On 4x4 vehicles, make sure the 4x4 selector is in the 2-wheel drive mode. Engage the driveline and accelerate to the observed road test speed to verify the presence of a vibration. If the vibration can be duplicated on the hoist, proceed to driveshaft inspection, Step 5. If the vibration does not occur, proceed as follows:
^ Carry out a careful visual inspection of the tire and wheels for wear or damage. Verify that the correct tire size and wheel rim is used. Verify that the tire pressure is correct. Refer to the tire manufacturer's specifications for the correct pressures. If a tire or wheel is damaged, carry out a careful visual inspection of the front or rear suspension components. The suspension can be worn, damaged or misaligned, contributing to the tire or wheel damage. Check the balance of the tires and wheels without the removal of the factory weights. Check the non-drive wheels first, and then the drive wheels. Repair as necessary. Repeat the road test. If a vibration still exists, proceed to Step 4.
4. Check the tire and wheel radial runout measurements with a dial indicator or tire runout gauge.
^ Place the stem of the gauge in a smooth area as close to the center tread as possible.
^ Rotate the tire to locate the low spot. Zero the indicator. Turn the tire and mark the high spot. Acceptable radial runout is 1.14 mm (0.045 inch) or less.
^ If the tire radial runout exceeds specification, check the wheel runout.
^ Place the stem of the gauge on the wheel outer diameter or bead seat.
^ Rotate the wheel to locate the low spot. Zero the indicator. Turn the wheel and mark the high spot. Acceptable wheel radial runout is 0.9 mm (0.035 inch) or less. Install a new tire or wheel as necessary.
Check the tire and wheel lateral runout measurements with a dial indicator or tire runout gauge.
^ Place the stem of the gauge on a smooth area of the tire as close to the tread as possible.
^ Rotate the tire to locate the low spot. Zero the indicator. Turn the tire and mark the high spot. Acceptable tire lateral runout is 1.14 mm (0.045 inch) or less.
^ If the lateral runout exceeds specification, check the wheel runout.
^ Place the stem of the gauge on the wheel face.
^ Rotate the wheel to locate the low spot. Zero the indicator. Turn the wheel and mark the high spot. Acceptable wheel lateral runout is 0.9 mm (0.035 inch) or less. Install a new tire or wheel as necessary.
Check the brake disc rotor (front and rear) and the rear axle shaft (drum brake) runout. Remove the tire and wheels and the brake drum.
^ Zero the indicator. Place the dial indicator stem against the flange face.
^ Turn the brake disc rotor or axle shaft one full revolution and read the total indicator movement. If the reading is above the acceptable limit, install a new rotor or axle shaft.
^ Check the wheel bolt runout by placing the dial indicator stem against the wheel bolt as close to the rotor face as possible. Zero the indicator and pull the indicator stem back. Rotate the hub to the next wheel bolt and release the stem. Continue until all wheel studs have been read. If the total runout exceeds specification, install a new hub/rotor.
5. Inspect the driveshaft(s) for damage, undercoating or incorrectly seated universal joints. Rotate the driveshaft slowly by hand and feel for binding or end play in the U-joint trunnions. Check the index marks (yellow paint) on the rear driveshaft and the pinion flange. If the marks are not aligned, disconnect the driveshaft and realign the marks as close as possible. Remove and inspect the slip yoke splines for any galling, dirt, rust or incorrect lubrication. Clean the driveshaft or install new U-joints as necessary. Install a new driveshaft if damaged. After any corrections or new components are installed, recheck for the vibration at the road test speed. If the vibration is gone, reinstall the tires and wheel and test drive. If the vibration persists or the driveshaft passes visual inspection, proceed to Step 6.
6. Using a dial indicator, measure the driveshaft at the front, center and rear. Rotate the shaft using a brake drum or brake disc rotor. If the runout exceeds 0.889 mm (0.035 inch) at the front or center, install a new driveshaft. If the front and center is within specification, but the rear runout is not, index mark the rear runout high point and proceed to Step 7. If the runout is within specification at all points, balance the driveshaft.
7. Index-mark the driveshaft to the pinion flange. Disconnect the driveshaft and rotate it 180 degrees. Reinstall the driveshaft. Recheck the runout at the driveshaft rear. If the runout is still over 0.889 mm (0.035 inch), mark the high point and proceed to Step 8. If the runout is within specification, check for the vibration at the road speed. If the vibration is still present, proceed to Step 9 to balance the driveshaft.
8. Excessive driveshaft runout can originate in the driveshaft itself To find the source, compare the 2 high points previously determined. If the index marks are close together, within 25 mm (1 inch), the driveshaft is eccentric. Install a new driveshaft. Recheck the driveshaft at the road test speed.
If the marks are on opposite sides of the driveshaft, 180 degrees apart, the slip yoke or pinion flange is responsible. Check the pinion flange runout. Refer to Pinion Flange Runout. Install a new pinion flange as necessary. Pinion Flange Runout Check - Circular
If the pinion flange runout exceeds 0.13 mm (0.005 inch), a bent pinion is indicated. Repair the ring and pinion as necessary. Road test the vehicle. If the pinion flange and pinion runouts are within specifications, road test and check for the vibration at the road test speed. If the vibration persists, balance the driveshaft.
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.
9. To balance the driveshaft, install 1 or 2 hose clamps on the driveshaft, near the ends. Position of the hose clamp head(s) can be determined through trial and error.
10. 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.
11. 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 11. 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.
12. 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 rear drive axle/differential - Ford 8.8 inch ring gear, rear drive axle/differential - Ford 9.75 inch ring gear or rear drive axle/differential - Ford 10.25 inch ring gear for differential case and ring gear runout checks.