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. Inspect the propeller shaft. The propeller shaft should be free of undercoating before continuing.
4. Inspect the propeller shaft and the U-joint for any obvious dents or damage. Dents or damage will contribute to first-order driveline vibrations.
5. Start the engine.
6. Place the transmission in gear.
7. Run the vehicle up to the speed at which the vibration was most severe.
8. Record whether the vibration was present, and at what speed.
9. If the vibration is not present, refer to Types of Road Test .
10. If the vibration is present, determine which end of the driveshaft is vibrating the most. Hold your hand against the transmission tailshaft, or hold an EVA vibration sensor up to each component.
11. The vehicle is equipped with a two-piece propeller shaft, inspect the center support bearing for vibration.
12. 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.
13. 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.

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:

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.

Tools Required

1. Raise the vehicle on a suitable hoist. Refer to Lifting and Jacking the Vehicle in General Information.
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.
6. 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.

6.1.	Measure the rear propeller shaft.

6.2.	Mark the position of the rear shaft in the pinion flange.

6.3.	Remove the rear shaft.

6.4.	Measure the front propeller shaft runout on the tube and the stub shaft.

6.5.	Replace the propeller shaft if either measurement is out of tolerance.

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.

First-order driveline vibrations that originate at the transmission end of the propeller shaft are rare. If the tailshaft of the transmission is vibrating, inspect the tailshaft housing bushing for wear or damage. A leaky transmission tailshaft oil seal indicates bushing problems.

Feel for vibration at the crossmember underneath the transmission mount. If there is no vibration, the transmission mount is functioning properly by isolating the vibration from the structure of the vehicle. The transmission mount is therefore probably not the cause of the vibration.

Use the following procedure if you can feel vibration on the crossmember and the tailshaft bushing, and if the transmission output is normal:

1. Measure the propeller shaft runout. If the runout is excessive, replace the shaft with one that has acceptable runout. Alternatively, sublet the shaft to a reputable independent service shop in order to have the shaft rebalanced and the runout corrected.
2. Test drive the vehicle. If the vibration is still unacceptable, balance the shaft on the vehicle. Proceed to Rear Driveline System Balance.

These guidelines apply to the two-piece propeller shaft only. First-order driveline vibrations that occur mainly at the center support bearing are usually the result of excessive runout at the stub (splined) shaft.

Unlike other first-order driveline vibrations, these vibrations can appear at unusually low speeds of 40 km/h (25 mph) and up.

Perform the following procedure in order to correct this type of vibration:

1. Mark the position of the rear propeller shaft at both ends for proper reassembly.
2. Remove the rear propeller shaft from the vehicle.
3. Measure the runout of the stub shaft splines (3) approximately 12.7 mm (0.5 in) from the end.
4. Replace the shaft if the runout exceeds the tolerances.

Stub shaft/spline runout 0.076 mm (0.003 in).

Correcting the stub shaft/spline runout will usually eliminate the vibration. If some residual vibration is still present, perform a road test on the vehicle. Determine if an on-vehicle system balance of the driveline is necessary.

The following procedure is designed to fine-tune the balance of the propeller shaft while it is mounted in the vehicle. This procedure will also correct residual imbalance of the remaining driveline components.

Prior to balancing the driveline system, verify that the propeller shaft and the pinion flange runout are within specification.

Important: Do not overheat the engine when performing this procedure.

1. Raise the vehicle to curb height. Support the vehicle on a hoist or on safety stands. Do not allow the axle to hang. 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. Determine which end of the propeller shaft has the most vibration in order to identify where to begin installing the hose clamps.



4. Mark the end of the propeller shaft (1) which has the most vibration at 4 points (2), 90 degrees apart. Number the marks 1-4.

The following procedure uses a trial and error method of determining where to place the hose clamps on the shaft. Use the following tips in order to help locate the clamps:

1. Because the imbalance may be related to propeller shaft runout, begin installing the clamps at the low point of the propeller shaft runout.
2. When the plant workers balance the propeller shaft, they use weights in graduated increments: 2 g (1/16 oz), 4 g (1/8 oz), etc. If the stock weight is too light or too heavy, place the hose clamp either directly in line with or opposite to the stock weight.

The last method involves running the vehicle at a speed which the vibration is felt.

1. Carefully hold a piece of chalk up to the very end of the propeller shaft. Barely touch the chalk to the shaft.
2. Shut the engine OFF in order to stop the propeller shaft from rotating. Do not step on the brake pedal. Do not put the transmission in PARK.
3. Inspect the chalk mark.

If you performed the above procedure correctly, the chalk mark will indicate the heavy spot on the shaft. The heavy spot will deflect downward and touch the chalk. If the chalk mark circles the entire shaft, touch the chalk more gently to the shaft. Ensure that the chalk touches only the heavy spot. Once the heavy spot is located, place the hose clamp 180 degrees opposite to the chalk mark (1). Perform the following steps:

1. Place the hose clamp at the light spot, or at any of the 4 points marked previously.
2. Test drive the vehicle at the speed at which the vibration occurred. Record any changes in the vibration.
3. Move the clamp to the other positions.
4. Test drive the vehicle each time you move the clamp. Record any changes in vibration. Remember which position gives the best balance.

•	If the vibration did not change at all or if the vibration becomes worse, then 1 clamp is either too light or too heavy. Repeat the procedure using the 2 clamps together (2).

•	If the previous step did not correct the problem, repeat the procedure using the 2 clamps separated in order to reduce the spinning weight.

Continue the trial and error procedure using different weights in different locations until you achieve the best balance. If more that 3 clamps aligned in the same position are required, replace the propeller shaft.

If you are able to reduce the vibration in the stall, but are unable to eliminate the vibration completely, perform a road test on the vehicle. A slight vibration noticeable in the stall may not be noticeable on the road.

In order to pinpoint the source, you must reproduce the vibration in the service stall. Determine which component is vibrating the most using the EVA. Perform the following steps:

1. Support the vehicle on a suitable hoist or on safety stands. Ensure that the rear of the rear axle is at curb height. Do not allow the axle to hang. 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. Ensure that the propeller shaft is free of undercoating. Inspect for dents or damage to the propeller shaft or the U-joint.
4. Start the engine.
5. Place the transmission in gear.
6. Run the engine at the vehicle speed at which the vibration is occurring.

Caution: Do not run the vehicle higher than 89 km/h (55 mph). Stay clear of the universal joints and the balance weight area in order to avoid personal injury. Do not run the vehicle on the hoist for extended periods of time. Running the vehicle on the hoist for extended periods of time may cause the engine or the transmission to overheat.

Determine which end of the propeller shaft is vibrating the most. Hold the EVA's sensor against the pinion nose and the transmission tailshaft assembly. The higher the amplitude reading, the greater the vibration.

Ensure that the runout of the various driveline components are within specifications. If the runouts are within specifications, strobe balance the driveline. The EVA is able to simplify the balancing process, using the following procedure:

1. Use the EVA in order to determine which end of the propeller shaft has the most vibration.



2. Mark the end of the propeller shaft (1) that has the most vibration at 4 points (2), 90 degrees apart. Number the marks 1-4.
3. Mount the EVA sensor onto the bottom of the following components:

•	The differential housing

•	The center bearing support (for 2-piece propeller shafts that use a center bearing support)

•	The transmission tailshaft assembly

4. Position the sensor as close to the propeller shaft as possible. Verify that the following conditions exist:

•	The UP side of the sensor faces upward.

•	The sensor is horizontal.

5. Start the engine.
6. Turn OFF all of the engine accessories.
7. Place the transmission in gear.
8. Run the vehicle at the speed which causes the most vibration in the propeller shaft.
9. Hook the timing light clip to the trigger wire.
10. Plug the vibration sensor into Input A of the EVA. Input B is not applicable for this test.
11. Verify that the predominant frequency on the EVA display matches the frequency of the original vibration. Use the strobe light only if the rotation speed of the propeller shaft is the predominant frequency.
12. The EVA displays a series of questions in order to select the correct filter. Press YES in order to select the desired filter. Ensure that the frequency is in the middle of the filter range. Use the full range only as a last resort.
13. The display shows the test frequency, the amplitude and the filter range. The driveline is balanced when the amplitude is near 2. In some cases, a slightly higher amplitude will provide adequate balance.
14. Point the timing light at the propeller shaft. The strobe effect will appear to freeze the propeller shaft. Remember which of the numbered marks is at the bottom of the propeller shaft, or the 6 o'clock position. This position is the light spot.
15. Turn the engine OFF.
16. Install a weight directly on the light spot.
17. Start the engine.
18. Run the vehicle at peak vibration speed.



19. Strobe the propeller shaft again.

•	The propeller shaft is balanced if the strobe image is erratic and the amplitude is near 2.

•	The propeller shaft is not balanced if one of the following conditions exist:

-	The weight and the original light spot are at the 6 o'clock position (1).

-	The above condition means that there is not enough weight on the propeller shaft. In order to correct the balance, add a second weight next to the first weight. Inspect the balance again using the strobe light.

-

If the weights are now 90-180 degrees off (between the 9 o'clock and the 3 o'clock positions) too much weight exists. In order to correct the balance, split the 2 weights equally on either side of the original light spot (1) in order to produce a total weight between 1-2 weights (between 0-120 degrees apart). Inspect the balance again using the strobe light. Adjust the weights as needed.

-	The weight and original light spot are 90-180 degrees off (between the 9 o'clock and the 3 o'clock positions).

-

The above condition means that 1 weight is too much. In order to correct the balance, split the 2 weights equally on either side of the original light spot in order to produce a total weight less than 1 (120-180 degrees apart). Inspect the balance again using the strobe light. Adjust the weights as needed.

-	The weight and the original light spot are within 180 degrees of the 6 o'clock position.

-	Move the weight towards the 6 o'clock position. Inspect the balance again using the strobe light. Adjust the weight as necessary. Refer to the previous 2 conditions.

If the shaft will not balance using 2 weights, place a third weight on the light spot. Split the first 2 weights in order to produce a total weight between 2 and 3 weights.

If 3 weights fail to balance the driveline, replace the propeller shaft.

When the propeller shaft balances, road test the vehicle in order to verify that the vibration is eliminated.

When using clamps in order to balance a propeller shaft with the total weight method, the correction weight required will often be a fraction or a multiple of one hose clamp. Use the following phasing procedure with 2 hose clamps in order to accurately place any required amount 0-2 weights (0.0-2.0 total weights).

1. Ensure that the clamps are located with even spaces on either side of the light spot, or 180 degrees opposite the heavy spot (1).

The table containing the weight amounts in terms of the total weight and the included angle (spread) between the clamps is in specifications.

2. If the vibration does not change at all or gets worse, then 1 clamp is too light or too heavy. Repeat the procedure using the 2 clamps together.
3. If the previous step did not correct the problem, repeat the procedure using the 2 clamps separated in order to reduce the spinning weight.
4. Continue the trial and error procedure using different weights in different locations until you achieve the best balance.
5. If more than 3 clamps aligned in the same position are required, replace the propeller shaft.
6. If you are able to reduce the vibration in the stall, but are unable to eliminate the vibration completely, road test the vehicle. A slight vibration that is noticeable in the stall may not be noticeable on the road.

If the following conditions are true, the internal rear axle components are the probable cause of the vibration:

Internal rear axle vibrations may be aggravated by the load of the vehicle working against the ring and pinion gear seat.

Since the propeller shaft and the pinion gear are bolted together through the pinion flange, the propeller shaft and the pinion gear operate at the same speed. Vibration in the pinion gear will therefore have the same frequency and symptoms as the propeller shaft.

In order to isolate the vibration to the pinion gear, use the following procedure:

1. Raise the vehicle to curb height. Support the vehicle on a hoist or on safety stands. Refer to Lifting and Jacking the Vehicle in General Information.
2. Remove the tire/wheel assemblies. Refer to Tire and Wheel Removal and Installation in Tires and Wheels.
3. Touch the pinion nose or hold the EVA vibration sensor up to the pinion nose.
4. With the aid of another technician, accelerate and decelerate the vehicle through the speed range at which the vibration was noticed during the road test.

Example

•	If the vibration was originally noticed at 88 km/h (55 mph), accelerate from 72 km/h (45 mph) to 107 km/h (65 mph). Then decelerate from 107 km/h (65 mph) back to 72 km/h (45 mph).

•	Repeat the above step and remember whether or not the pinion nose vibrates under load during acceleration and/or deceleration.

If the vibration does not occur during the above procedure, install the tire/wheel assemblies, adding additional load on the system. Then repeat the above test.

Ensure that both axle shafts rotate at the same speed. The differential may mask a vibration when one tire is spinning faster than the other tire. Adjust the brakes in order to correct unequal tire rotation speed.

If you are unable to reproduce the vibration in the stall, apply the brake lightly in order to load the system further. Maintain the vehicle speed at which the vibration was noticed. Do not overheat the brakes.

If the pinion nose vibrates under acceleration and/or deceleration, and the other driveline components are eliminated as the cause of the vibration, then one of the following conditions may cause the vibration:

Anything that effects the pinion gear and how the pinion gear contacts the rotating ring gear may contribute to a first-order, torque-sensitive driveline vibration. The only way to correct the condition is to replace the faulty components. In most cases, you must replace the ring and pinion gear set and the related bearings. In some cases, you must replace the axle housing. Complete a close-up visual inspection for damage or unusual wear in order to measure or identify the specific faulty component.

It is possible to isolate an internal axle vibration. Install a known good axle assembly from a stock unit. Verify that the known good axle assembly does not have a vibration problem.

Once you correct the internal axle problem, road test the vehicle. Inspect the vehicle for vibration. Balance the driveline, as necessary, in order to eliminate any remaining vibration.