Component Tests and General Diagnostics

Driveline System

Component Tests

Axle Vent

A plugged vent will cause excessive seal lip wear due to internal pressure buildup. If a leak occurs, check the vent. Make sure the vent hose is not kinked. Remove the hose from the vent nipple and clear the hose of any foreign material. While the hose is removed, pass a length of mechanic's wire or a small diameter Allen wrench in and out of the vent to clean it. Connect the hose when done.


Traction-Lok(R) Differential Operation Check

A Traction-Lok(R) differential can be checked for correct operation without removing it from the rear axle housing.

Raise only one rear wheel. Install the Differential Clutch Gauge on the wheel bolts.





Use a torque wrench with the capacity of at least 271 Nm (200 lb-ft) to rotate the axle shaft. Be sure that the transmission is in NEUTRAL, and that one rear wheel is on the floor while the other rear wheel is raised off the floor. The breakaway torque required to start rotation must be at least 27 Nm (20 lb-ft). The initial breakaway torque may be higher than the continuous turning torque.





The axle shaft must turn with even pressure throughout the check without slipping or binding. If the torque reading is less than specified, check the differential case. Refer to Rear Drive Axle/Differential - Ford 8.8-Inch Ring Gear Testing and Inspection.


Traction-Lok(R) Differential Check Road Test

1. Place one wheel on a dry surface and the other wheel on ice, mud or snow.

2. Gradually open the throttle to obtain maximum traction prior to break away. The ability to move the vehicle demonstrates correct operation of a Traction-Lok(R) rear axle assembly.

3. When starting with one wheel on an excessively slippery surface, a slight application of the parking brake may be necessary to help energize the Traction-Lok(R) feature of the differential. Release the brake when traction is established. Use light throttle on starting to provide maximum traction.

4. If, with unequal traction, both wheels slip, the limited slip rear axle has done all it can possibly do.

5. In extreme cases of differences in traction, the wheel with the least traction may spin after the Traction-Lok(R) has transferred as much torque as possible to the non-slipping wheel.


Pinion Flange Runout Check - Circular

1. Check the pinion flange for damage.

2. Position Drive Pinion Flange Runout Gauge on the pinion flange.











3. Position the Driveshaft Clamp Plate onto the Drive Pinion Flange Runout Gauge.






4. Align the holes on the Driveshaft Clamp Plate with the holes in the pinion flange and install the bolts. Snug the bolts evenly.






5. Position the Dial Indicator Gauge with Holding Fixture as shown. Turn the Drive Pinion Flange Runout Gauge, and locate and mark the high spot on the pinion flange with yellow paint.






6. If the flange runout exceeds 0.25 mm (0.010 in), remove the pinion flange, re-index the flange one-half turn on the pinion, and reinstall it. Refer to Rear Drive Axle/Differential - Ford 8.8-Inch Ring Gear Service and Repair.

7. Check the runout again. If necessary, rotate the flange until an acceptable runout is obtained. If the flange runout is still more than 0.25 mm (0.010 in), install a new pinion flange.






8. If excessive runout is still evident after installation of the pinion flange, install a new ring and pinion. Repeat the above checks until the runout is within specifications.