Part 1

Diagnosing First-Order Driveline Vibration

Diagnosis will be much easier once you have identified a vibration as first-order of driveline rotation during the road test. Next identify the exact area of the vibration and take proper action.


In most cases, vibration may be reproduced in the stall. In the stall the vibration may be better or worse than that experienced during the road test.


The objective is to reduce the vibration to the lowest point possible in the stall, then evaluate the results during a road test. Many times, a vibration you were only able to reduce drastically in the stall will be completely eliminated on the road.


The cause of first-order driveline vibration is usually excessive runout or an imbalanced component.


The following procedure offers a systematic process of elimination in order to determine which component is at fault:

1. Raise the vehicle to curb height. Support the vehicle on a hoist or heavy stands. Refer to Lifting and Jacking the Vehicle in General Information.
2. Remove the rear tire/wheel assemblies. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.
3. Remove the brake drums. Refer to Brake Drum Replacement in Drum Brakes.
4. Inspect the propeller shaft. The propeller shaft should be free of undercoating before continuing.
5. Inspect the propeller shaft and the U-joint for any obvious dents or damage. Dents or damage will contribute to first-order driveline vibrations.
6. Start the engine.
7. Place the transmission in gear.

Important: Do not step on the brake while the brake drums are being removed.


8. Run the vehicle up to the speed at which the vibration was most severe.
9. Record whether the vibration was present, and at what speed.
10. If the vibration is not present, refer to Types of Road Test Procedures.
11. If the vibration is present, determine which end of the driveshaft is vibrating the most. Hold your hand against the pinion nose and the transmission tailshaft, or hold an EVA vibration sensor up to each component.
12. If the vehicle is equipped with a two-piece propeller shaft, inspect the center support bearing for vibration.
13. If the transmission tail is vibrating, touch the transmission crossmember under the transmission mount. If there is no vibration on the crossmember, then the transmission mount is working properly.
14. Remember which end of the driveshaft is the worst, and how severe the vibration is. The inspection will be a reference by which to judge future progress.


Do not fill the propeller shaft with foam, oil, or any other substance in order to correct a vibration. Filling the propeller shaft is only effective in reducing an unrelated condition called Torsional Rattle. Filling the propeller shaft should only be done in strict adherence to the procedure outlined in corporate bulletins that address Torsional Rattle. Failure to follow the correct procedure will induce a vibration and/or affect the structural integrity of the propeller shaft. The propeller shaft will then have to be replaced.


Propeller Shaft Runout

A propeller shaft or pinion (companion) flange with excessive runout causes first-order driveline vibrations. Use the following procedure in order to measure the runout of the propeller shaft:

* Remove excess corrosion of the propeller shaft surface before inspecting the runout.
* Inspect for damage and dents.
* Replace dented propeller shafts.
* Remove any undercoating from the propeller shaft before proceeding.
* Refer to Measuring Propeller Shaft Runout, below, for the measurement procedure that applies to the following shaft assemblies:

- One-piece
- Two-piece



The splined end of a propeller shaft is critical to the smooth operation of a two-piece propeller shaft. When inspecting stub-shaft runout, ensure that the dial indicator readings are accurate.


Measuring Propeller Shaft Runout


Tools Required
* J 8001 Dial Indicator Set
* J 7872 Magnetic Base Dial Indicator Set





1 - Slip Yoke
2 - Tube
3 - Rear Runout Check
4 - Center Runout Check
5 - Front Runout Check
6 - Damper

1. Raise the vehicle on a suitable hoist. Refer to Lifting and Jacking the Vehicle in General Information. Refer to Lifting and Jacking the Vehicle
2. Allow the wheels to spin freely.




3. Attach a J 8001 and a J 7872 .
4. Place the transmission in NEUTRAL.
5. Rotate the pinion flange or the transmission yoke by hand while taking the measurements for the runout.

Important: The propeller shaft turns easier in 1 direction than in the other. Removing the wheels and the drums will also help. Do not include fluctuations on the dial indicator due to welds or surface irregularities.


6. Perform the following steps for one-piece propeller shafts if the runout exceeds the tolerances at 1 or more points:

1. Rotate the propeller shaft 180 degrees in the pinion flange.
2. Reinstall the propeller shaft.
3. Measure the propeller shaft runout.
4. If the runout still exceeds the tolerance, inspect the pinion flange runout before replacing the propeller shaft.

7. Perform the following steps for 2-piece propeller shafts if the runout exceeds the tolerances at 1 or more points:


Important: The runout of the rear splines on the front propeller shaft affects the runout of the front measurement on the rear propeller shaft.


1. Measure the rear propeller shaft.
2. Mark the position of the rear shaft in the pinion flange.
3. Remove the rear shaft.
4. Measure the front propeller shaft runout on the tube and the stub shaft.
5. Replace the propeller shaft if either measurement is out of tolerance. Refer to Propeller Shaft Runout Specifications.



Important: When you replace a propeller shaft, inspect the new shaft for runout. Inspect the pinion flange runout if the replacement shaft runout is also out of tolerance.








Measuring Pinion Flange Runout


Tools Required
* J 8001 Dial Indicator Set
* J 23409 Dial Indicator Extension
* J 35819 Flange Runout Gauge


1. Place the vehicle on a suitable hoist. Refer to Lifting and Jacking the Vehicle in General Information. Allow the wheels to rotate freely.
2. Remove the propeller shaft from the pinion flange.




3. Install the J 35819 .
If a J 35819 is not available, measure the pinion runout as close as possible to the pinion flange.

Important: The dial indicator will have inverted readings. You are measuring the inside diameter of the flange; you are not measuring the outside diameter. The highest reading on the dial indicator is the low spot. The lowest reading is the high spot.


4. Rotate the pinion shaft 360 degrees and zero the dial indicator on the low spot.
5. Rotate the pinion flange again and record the total runout.
6. If the pinion flange runout is 0.15 mm (0.006 in) or less, remove the pinion flange balance weight.
7. If the pinion flange runout is greater than 0.15 mm (0.006 in) but not less than 0.28 mm (0.011 in), and the runout compensation weight is at or near the low spot, no further action is necessary. If the runout compensation weight is not at or near the low spot, remove the weight.
8. If the pinion flange runout is greater than 0.28 mm (0.011 in) but not greater than 0.38 mm (0.015 in), and the balance weight is at or near the low point, no further action is necessary. If the runout compensation weight is not at or near the low spot, remove the weight and re-index the pinion flange until the runout is 0.25 mm (0.010 in) or less.
9. Replace the pinion flange/yoke when the runout cannot be reduced to 0.25 mm (0.010 in) or less. Then, recheck the runout. Service replacement flanges do not have balance weights.






* If necessary, add compensation weights on the face of the pinion flange dust slinger. These weights are tack-welded onto the slinger. You may remove the weights with a die-grinder.
* Carefully remove the spot weld at either end of the weight.
* Do not remove the weight unless you have inspected the pinion flange runout and the procedure requires weight removal.
* Do not remove any weights on the outboard edge of the dust slinger. These weights are present in order to balance internal axle components. The weights are not related to the pinion flange runout.
* If a J 35819 is not available, inspect the propeller shaft runout as near as possible to the flange. Rotate the shaft 180 degrees in the pinion flange. Reinstall the shaft. Inspect the measurement at the same location.
A large difference in the runout, greater than 0.38 mm (0.015 in), may indicate that the flange is out of tolerance. If the runout does not change at all, the flange is OK.



Balanced Axles

Beginning in the early 1990's, the manufacturer began system balancing rear axles. During the build process, these axle assemblies were spun with a slave fixture. A balance weight was attached to the outboard edge of the companion flange dust slinger. A system-balanced rear axle companion flange differs from a non-balanced flange. You must diagnose and service this flange in a unique way.





Some pinion flange assemblies have a U-shaped deflector designed to hold a system balance weight on the outside diameter.





Other pinion flange assemblies have a runout compensation weight on the face of the deflector. The pinion flange assemblies that are system balanced do not use runout compensation weights.


Measuring the runout on a system-balanced companion flange is very straight-forward. A balanced flange that is good will have a measured runout between 0.00-0.38 mm (0.00-0.015 in). If a balanced flange has more than 0.38 mm (0.015 in) runout, replace the flange or reindex the flange 180 degrees on the pinion. If you replace or reindex a balanced flange, you must system balance the rear axle again.


Correcting Vibration at the Pinion Nose

Most first-order driveline vibrations originate at the pinion nose end of the driveshaft. Ensure that the vibrations are at a minimum at this location in order to achieve acceptable results. Reduce the runout of the components to a minimum. Balance the driveline as a system when necessary.

1. Measure the runout of the propeller shaft and inspect the tolerance.
2. If the tolerance is excessive, mark the position of the shaft for future reference and rotate the shaft 180 degrees.
3. Reinstall the shaft and reinspect the runout. Inspect the level of vibration in order to determine if the vibration is lower or corrected.
4. If the runout is still excessive, or if the vibration is still present, refer to Measuring Pinion Flange Runout. Replace the pinion flange or re-index the flange 180 degrees if the pinion flange runout exceeds the tolerance.
Remove and reinstall the pinion flange only once on axles utilizing a crush type sleeve. Replace the sleeve with a new sleeve if the sleeve is crushed. Removing the sleeve requires removal of the ring and pinion set. Replace flanges with excessive runout. Regardless of the method used, measure the pinion flange runout in order to ensure that the flange is within tolerance.
5. Reinspect the propeller shaft runout if the vibration is present after the pinion flange runout is corrected. If the propeller shaft runout is still excessive, correct the runout before doing a driveline system balance. Either replace the shaft with a shaft that is within tolerance or sublet the shaft to a reputable independent for straightening and re-balance. Ensure that the new or rebuilt shaft is within runout tolerance before continuing.
6. Once the propeller shaft and pinion flange are within runout tolerances, inspect to see if the vibration is still present. If the level of the vibration is still unacceptable, perform a driveline system balance procedure.