Analysis of Vibration
Few vibration conditions are caused by the rear axle. On a vibration concern, follow the diagnosis procedure unless there is a good reason to suspect the axle.Tires
WARNING: Do not balance the wheels and tires while they are mounted on the vehicle. Possible tire disintegration/differential/halfshaft failure could result, causing personal injury/extensive component damage. Use an off-vehicle wheel and tire balancer only.
Most vibration in the rear end is caused by tires or driveline angle.
Vibration is a concern with modern, high-mileage tires if they are not "true" both radially and laterally. They are more susceptible to vibration around the limits of radial and lateral runout of the tire and wheel assembly. They also require more accurate balancing.
Wheel and tire runout checks, truing and balancing are normally done before axle inspection.
Driveline Angle
Driveline angularity is the angular relationship between the engine crankshaft, the driveshaft, and the rear axle pinion. Factors determining driveshaft center bearing height, rear axle, and engine/transmission mounts.
An incorrect driveline (pinion) angle can often be detected by the driving condition in which the vibration occurs.
- A vibration during coasting from 72 to 56 km/h (45 to 35 mph) is often caused by a high axle pinion angle.
- A vibration during acceleration from 56 to 72 km/h (35 to 45 mph) may indicate a low pinion angle.
When these conditions exist, check the driveline angles.
If the tires and driveline angle are not the cause, carry out the NVH tests to determine whether the concern is caused by a condition in the axle.
Driveline Angle Check
CAUTION: When carrying out operations which involve the removal and installation of the driveshaft, always check the joint angles and make the necessary adjustments.
1. Park the vehicle on a level surface such as an alignment rack or a drive-on hoist.
2. Remove the exhaust heat shield fasteners and slide the exhaust heat shield as far forward as possible to expose the driveshaft-to-axle coupling.
3. Rotate the driveshaft several times by hand to neutralize the center support bearing and flex couplings.
4. Zero the special tool.
1 Place the special tool on the left frame rail with the special tool facing the passenger side.
2 Zero the special tool using the thumbscrew.
3 Mark the location where the special tool was zeroed with a paint pen.
5. Note: The special tool contacts the flex coupling bolt sleeve to obtain an accurate reading.
Note: The bolt should never be removed, only the nut.
Make preparations to measure the transmission angle (A) with respect to the frame rail.
1 Remove one of the nuts that attaches the flex coupling to the transmission flange.
2 Install the special tool onto the bolt on the rear of the flex coupling and tighten the nut.
6. Place the special tool in the bracket slot with the special tool facing the passenger side and record the reading.
- Remove the special tools and tighten the fastener to specification.
7. Note: The special tool must contact the flex coupling bolt sleeve to obtain an accurate reading.
Note: The bolt should never be removed, only the nut.
Make preparations to measure the front driveshaft angle (B) with respect to the frame rail.
1 Remove one of the nuts that attaches the flex coupling to the front driveshaft.
2 Install the special tool onto the bolt on the front of the flex coupling and tighten the nut.
8. Place the special tool in the bracket slot with the special tool facing the passenger side and record the reading.
- Remove the special tools and tighten the fastener to specification.
9. Note: The special tool must contact the flex coupling bolt sleeve to obtain an accurate reading.
Note: The bolt should never be removed, only the nut. Make preparations to measure the rear driveshaft angle (C) with respect to the fume rail.
1 Remove one of the nuts that attaches the flex coupling to the rear driveshaft.
2 Install the special onto the bolt on the rear of the flex coupling and tighten the nut.
10. Place the special tool in the bracket slot with the special tool facing the passenger side and record the reading.
- Remove the special tools and tighten the fastener to specification.
11. Note: The special tool must contact the flex coupling bolt sleeve to obtain an accurate reading.
Note: The bolt should never be removed, only the nut.
Make preparations to measure the differential pinion angle (D) with respect to the frame rail.
1 Remove one of the nuts that attaches the flex coupling to the pinion flange.
2 Install the special tool onto the front of the flex coupling and tighten the nut.
12. Place the special tool in the bracket slot with the special tool facing the passenger side and record the reading.
- Remove the special tools and tighten the fastener to specification.
13. Calculate the angles of joints 1, 2 and 3 as follows:
- A-B=Joint 1
- B-C=Joint 2
- C-D=Joint 3
14. Note: To adjust the center support bearing adjusting washers, the exhaust heat shield must be removed.
Note: Left and right washers should be the same thickness.
Note: Two washers should not be assembled together.
Adjust the joint angles if necessary by varying the center support bearing adjusting washers.
15. Install the exhaust heat shield.
Wheel Hub Flange Bolt Circle Runout
Note: The brake discs must be removed to carry out all runout measurements.
1. Position the special tool perpendicular to the wheel hub bolt, as close to the hub face as possible. Zero the indicator to allow the pointer to deflect either way.
2. Rotate the hub until the next bolt is contacted. Record the measurement and continue until each bolt is checked. The difference between the maximum and minimum contact readings will be the total wheel hub bolt pattern runout. The runout must not exceed 0.38 mm (0.015 inch).
Pilot Runout
1. Position the special tools as close to the hub face as possible. Zero the indicator to allow the pointer to deflect either way.
2. Rotate the hub one full turn and note the maximum and minimum readings. The difference between the maximum and minimum readings will be the total pilot runout. Pilot runout must not exceed 0.15 mm (0.006 inch).
Wheel Hub Face Runout
1. Position the special tool on the wheel hub face, as close to the outer edge as possible. Zero the indicator to allow the pointer to deflect either way.
2. Rotate the hub one full turn and note the maximum and minimum readings. The difference between the maximum and minimum readings will be the total face runout. The runout must not exceed 0.254 mm (0.010 inch).
Drive Pinion Stem and Pinion Flange
Check the pinion flange runout when all other checks have failed to show the cause of vibration.
One cause of excessive pinion flange runout is incorrect installation of the axle drive pinion seal.
Check to see if the spring on the seal lip has been dislodged before installing a new ring gear and pinion.
Halfshafts, Rear Wheel
Note: Install new constant velocity (CV) joints only if disassembly and inspection reveals unusual wear.
Note: While inspecting the boots, watch for indentations ("dimples") in the boot convolutions. Indentations must be removed.
- Inspect the boots for evidence of cracks, tears, or splits.
- Inspect the underbody for any indication of grease splatter near the boots outboard and inboard locations. This is an indication of boot/clamp damage.