Initial Inspection
Driveline System
Special Tool(s)
Inspection and Verification
Certain axle and driveline symptoms are also common to the engine, transmission, wheel bearings, tires, and other parts of the vehicle. For this reason, be sure that the cause of the trouble is in the axle before disassembling, adjusting or repairing the axle.
Certain driveshaft vibration symptoms are common to the Front Accessory Drive (FEAD), the engine, transmission or tires. Be sure the cause is the driveshaft before repairing or installing a new driveshaft.
Certain symptoms may be caused by Traction-Lok differentials. Check the vehicle certification label and axle identification tag to determine the type of differential.
Noise Acceptability
NOTE: A gear-driven unit will produce a certain amount of noise. Some noise is acceptable and audible at certain speeds or under various driving conditions such as a newly paved blacktop road. Slight noise is not detrimental to the operation of the axle and is considered normal.
With the Ford Traction-Lok differential, slight chatter noise on slow turns after extended highway driving is considered acceptable and has no detrimental effect on the locking differential function.
Universal Joint (U-Joint) Inspection
Place the vehicle on a frame hoist and rotate the driveshaft by hand. Install a new U-joint if it shows signs of seizure, excessive wear, or incorrect seating.
Inspection For Bent Rear Axle Housing
1. Raise and support the vehicle. Allow the rear axle to be freely suspended.
2. Use white chalk or paint to mark a vertical line on the center of each rear tire.
3. Adjust both wheels so that the markings face the front of the vehicle. With a tape measure, measure the distance between the marks and record this reading (front reading).
4. Rotate the rear wheels so the markings are directly underneath the vehicle. Measure the distance between the marks and record this reading (bottom reading).
5. Rotate the rear wheels so the markings face the rear of the vehicle. Measure and record the distance between the marks (rear reading).
6. Compare the front and the rear readings (Steps 3 and 5) to find the toe-in or toe-out condition.
^ Toe-in occurs when the front measurement is less than the rear measurement.
^ Toe-out occurs when the rear measurement is less than the front measurement.
7. To determine camber, find the average of the front and the rear measurements (Steps 3 and 5). Subtract the bottom reading (Step 4) from this number.
8. Positive (+) camber is when the bottom reading is less than the average of the front and rear readings. Negative (-) camber is when the bottom reading is greater than the average of the front and rear readings.
9. The results of the calculations in Steps 6 and 7 must conform to the following specifications:
Toe-in: 0 - 1/16 inch.
Toe-out: 0 - 3/16 inch.
Camber: 0 ± 5/32 inch.
If the differential housing does not meet these specifications, install a new differential housing.
Analysis of Leakage
Clean up the leaking area enough to identify the exact source. An axle leak can be caused by the following:
^ Axle lubricant level is too high.
^ Worn or damaged axle shaft seals or differential seals.
^ Differential housing is cracked.
^ Flange yoke seal is worn or damaged.
^ Pinion flange is scored or damaged.
^ Axle cover is not sealed.
^ Vent is plugged.
Repair the axle as necessary. Make sure the axle lubricant is at the correct level. Refer to Specifications.
Axle Vent
NOTE: If a plugged vent cannot be cleared, install a new vent.
A plugged vent or vent hose will cause excessive seal lip wear due to internal pressure buildup. If a leak occurs, check the vent and the vent hose. Remove the hose from the vent nipple and clear the hose of any foreign material. While the hose is removed, pass a length of mechanics wire or a small diameter Allen wrench in and out of the vent to clean it. Connect the hose when done.
Flange Yoke Seal
Leaks at the axle drive pinion seal originate for the following reasons:
^ Seal was installed incorrectly.
^ Poor quality seal journal surface.
Any damage to the seal bore (dings, dents, gouges, or other imperfections) will distort the seal casing and allow leakage past the outer edge of the axle drive pinion seal.
The rubber lips can occasionally become hard and crack at the oil lip contact point. The contact point on the pinion flange may blacken. Marks, nicks, gouges, or rough surface texture on the seal journal of the pinion flange will also cause leaks.
Install a new pinion flange if any of these conditions exist.
When a seal leak occurs, install a new seal and check the vent and the vent hose to verify that they are clean and free of foreign material.
Wheel Hub Oil Seals
Wheel hub oil seals are susceptible to the same kinds of damage as axle drive pinion seals if installed incorrectly. The seal bore must be clean and the lip handled carefully to avoid cutting or tearing it. Spindle journal surface must be free of nicks, gouges, and rough surface texture.
Analysis of Vibration
WARNING: A vehicle equipped with a Ford Traction-Lok differential or a Tractech(R) Truetrac(R) differential will always have both wheels driving. If only one wheel is raised off the floor and the rear axle is driven by the engine, the wheel on the floor could drive the vehicle off the stand or jack. Verify that both rear wheels are off the floor.
Few vibration conditions are caused by the front or rear axle. On a vibration concern, follow the diagnosis procedure in Vehicle/Testing and Inspection 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 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 modem, 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 an axle inspection.