For 1990-2009 cars

The following components are possible sources of driveline vibration:

• | The transmission output shaft

• | The propeller shaft/s (driveshaft/s)

• | The union flange

• | The pinion gear

The above components are either bolted or splined together. Therefore, all of the components rotate at the same speed, vibrate at the same frequency and have the same symptoms.

Driveline vibrations may relate either to the first or to the second order of driveline rotation. Driveline vibrations are always related to the speed of the vehicle. The vibration is often related to torque. If the vibration is worse or only noticeable when accelerating, decelerating, or crowding the throttle, then the vibration is related to the torque. The vibration will always occur at the same speed. If a vibration is both torque and speed sensitive, the driveline is the probable cause. Tire/wheel vibrations are speed sensitive, but not torque sensitive.

### First-Order Driveline Vibration Symptoms

The following symptoms may indicate first-order driveline vibration:

• | The vibration is related to vehicle speed.

• | The vibration is torque sensitive.

• | A "boom" or "moan" noise is present.

• | The vibration occurs commonly above 72 km/h (45 mph), but possibly as low as 48 km/h (30 mph).

• | The "roughness" or "buzz" vibration is felt in the seat, floor or steering wheel.

• | The corresponding frequency on the EVA equals first-order driveline rotation (25-60 Hz), depending on the speed of the vehicle and the ratio of the axle. Refer to the worksheet in order to obtain the rotation speed of the propeller shaft.

### Driveline Vibration Analysis

Once you identify a vibration that is related to the driveline, continue testing in this service area. The following components are possible sources of first-order driveline vibration:

• | The propeller shafts

• | The transmission output shaft

• | The pinion flange

• | The pinion gear

### Locate the Source of Driveline Vibration with the EVA

Caution: Never run the vehicle faster than 112 km/h (70 mph) when performing propeller shaft vibration or checking for balance. Stay clear of rotating components and balance weights to avoid personal injury. Do not run the vehicle on the hoist for extended periods of time to avoid engine or transmission overheating. Do not step on the brake pedal with the brake drums removed.

In order to pinpoint the source of vibration, reproduce the vibration with the vehicle in the service stall. Then determine which component is vibrating the most using the EVA and the following 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
2. Remove the rear tire/wheel assemblies. Refer to Lifting and Jacking the Vehicle
3. Ensure that the propeller shaft is free of undercoating.
4. Inspect the propeller shaft and U-joints for dents or damage.
5. Start the engine.
6. Place the transmission in gear.
7. Run the vehicle at the speed which the vibration occurs.

Hold the EVA sensor against the pinion nose and the transmission tailshaft assembly in order to determine which end of the propeller shaft has the most vibration. The end that has the most vibration will have a higher amplitude on the EVA.

If the vehicle has a two-piece propeller shaft, inspect the center support bearing.

If the transmission tailshaft vibrates, inspect the transmission crossmember under the transmission mount. If the mount is secured properly, there should be no vibration at the crossmember.

### Runout and Balance Testing with the EVA

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. Use 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 four points (2), 90 degrees apart. Number the marks 1 through 4.
3. Mount the EVA sensor onto the bottom of the following components:

• | The differential housing

• | The center bearing support (for two-part propeller shafts)

• | The transmission tailshaft assembly

4. Position the sensor as close to the propeller shaft as possible. Ensure that the UP side of the sensor faces up. Ensure that the sensor is horizontal.

Notice: Do not use cruise control to maintain vehicle speed.

5. Start the engine.
6. Turn off all 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 does not have strobe light capability.
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 EVA displays the test frequency, the amplitude and the filter range. The driveline is balanced when the amplitude is near two. 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. Note which of the numbered marks is at the bottom of the propeller shaft (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 two.

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 -- This 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 between 90 and 180 degrees off (between the 9 and the 3 o'clock positions) there is too much weight. In order to correct the balance, split the two weights equally on either side of the original light spot. Splitting the weight will produce a total weight between one and two weights.

| Inspect the balance again using the strobe light. Adjust the weights as necessary.

• | The weight and original light spot are 90 to 180 degrees off (between the 9 and the 3 o'clock positions) -- This condition means that one weight is too much.

| In order to correct the balance, split the two weights equally on either side of the original light spot. in order to produce a total weight less than one (between 120 and 180 degrees apart).

| Inspect the balance again using the strobe light. Adjust the weights as necessary.

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

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

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

If three 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.

### First-Order Driveline Vibration Analysis (Torque Sensitive)

If the vehicle has a vibration that is equal to first-order driveline rotation, and the vibration is not present when testing the vehicle in the stall, then internal rear axle components are the probable cause of the vibration.

Internal rear axle components are also the probable cause of the vibration if you were able to correct the vibration in the stall, but the vibration returned during the road test. 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 Wheel Removal in Tires and Wheels.
3. Remove the brake drums.
4. Touch the pinion nose, or hold the EVA vibration sensor up to the pinion nose.
5. Use another technician in order to 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 note 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 brake drums and the tire/wheel assemblies. The brake drums and tire/wheel assemblies will add 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:

• | A high spot on the pinion gear

• | A bent pinion stem

• | A cocked pinion bearing

• | An improper axle housing bore

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, the ring and pinion gear set and the related bearings must be replaced. In some case, however, the axle housing must be replaced. 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.

### Second-Order Driveline Vibration Theory

A faulty universal joint (U-joint) may cause a vibration that occurs twice for each rotation of the propeller shaft. This type of vibration is called a second-order vibration.

Second-order driveline vibrations are independent of runout or balance of a driveline component.

The following description of basic U-joint theory will help you to understand where second-order driveline vibrations originate and why they occur.

• | As the propeller shaft rotates, the U-joints speed up and slow down twice for each rotation of the propeller shaft.

• | The acceleration and deceleration of the U-joints is not visible. If there is vibration in the U-joints, the acceleration and deceleration will be audible and tactile.

• | Compare the U-joint in a vehicle to a universal-type socket. When a universal-type socket is used to tighten a bolt, the socket will "bind and release" as the socket turns toward 90 degrees. The "bind and release" occurs twice for each revolution of the socket.

• | The U-joint in a vehicle works in the same way as the universal-type socket. The "bind and release" effect is directly proportional to the angle that the U-joint operates: the greater the angle, the greater the effect.

• | Because the transmission output speed is constant, the binding and releasing of the U-joints is better described as an acceleration and deceleration which occurs twice for each revolution of the propeller shaft.

• | If the propeller shaft is running slowly, the accelerating and decelerating effect is visible. The acceleration and deceleration may create a vibration due to the fluctuations in force that are generated at high speeds.

#### Canceled Out Driveline Angles

(1) | Front Working Angle
(2) | Rear Working Angle

Engineers design drivelines in order to compensate for the accelerations and decelerations in order to produce a smooth, constant flow of power, as listed below:

• | The transmission drives the front yoke of the propeller shaft at a smooth and constant speed.

• | The first U-joint causes the power to fluctuate twice for each revolution of the propeller shaft .

• | The second U-joint, oriented 90 degrees from the first U-joint, causes the power to fluctuate opposite that of the first U-joint .

• | As the first joint slows down, the second joint speeds up.

This design causes one U-joint to cancel out the effect of the other U-joint. The cancelled effects result in a smooth, constant power flow from the output yoke of the propeller shaft.

Second-order driveline vibrations occur when the cancellation become unequal between the front and rear U-joints.

### Second-Order Driveline Vibration Symptoms

Second-Order driveline vibration has the following signs and symptoms:

• | The vibration is always related to vehicle speed.

• | The vibration is usually torque-sensitive.

• | The vibration is worse under a torque load.

Launch shudder is the most common complaint of a second-order driveline vibration.

Launch shudder occurs during acceleration from 0-40 km/h (0-25 mph). Launch shudder appears as a low frequency shake, wobble, or shudder. The driver may feel the vibrations in the seat or steering wheel at low speeds [0-24 km/h (0-15 mph)]. The vibrations will increase in frequency as the vehicle speed increases. Launch shudder feels more like driveline roughness at higher speeds [24-40 km/h (15-25 mph)]. At speeds greater than 40 km/h (25 mph) the vibration usually disappears.

Launch shudder vibration is equal to a second-order vibration of the driveline. The EVA will not perceive frequency information due to the transitory nature of launch shudder.