Tools Required

J 39704 Dial Indicator

Important: Both methods for setting differential bearing preload and gear backlash are described. All Model 80 axle assemblies can be serviced by using the outboard selective shim method.

Notice: If the original axle assembly has the outboard selective shims, it should not be serviced using the inboard shims for preload/backlash adjustment. In other words, if you have outboard selective shims, you must stay with that method. If the axle assembly uses in board shims and outboard spacers (non-selective), you may use the outboard selective shim method for service.

Notice: If your axle assembly has selective outboard spacers and one 0.76 mm (0.030 inch) shim (each side) between the differential case and bearing cone. Make your measurements with the outboard spacers removed, but with the 0.76 mm (0.030 inch) shim assembled on the differential case trunion placed between the case and the master differential bearings. The selective outboard spacers are available in sizes (thickness) from 5.18 mm (0.2040 inch) to 6.10 mm (0.2400 inch), in 0.08 mm (0.003 inch) increments. The dial indicator should have the capability of making measurements up to 12.7 mm (0.500 inch).

Notice: If your axle assembly has outboard spacers, but controls the preload and backlash by using selective shims (each side) between the differential case and bearing cone. Make the measurements with the outboard spacers installed in the housing, but do not place any shims on the differential case hubs between the case and master differential bearings. The selective shims placed between the bearing cone and differential case are available in 0.08, 0.13, 0.25, 0.76 mm (0.003, 0.005, 0.010, 0.030 inch) sizes. The dial indicator should have the capability of making measurements up to 3.81 mm (0.150 inch).

1. Assemble the case to the axle housing. The pinion must not be installed.



2. Mount the J 39704 on the ring gear bolt side of the differential housing.
3. Force the differential assembly as far as possible in the direction of the J 39704 .
4. Preload the J 39704 one half of its travel.
5. Place the tip of the J 39704 on a flat surface of the differential next to a ring gear bolt.
6. Mark with chalk the location of the tip of the J 39704 .
7. Zero the dial indicator.
8. Force the differential case as far as possible in the direction away from the J 39704 . Repeat this step until the same reading is obtained.
9. Record the number of thousandths that the dial indicator traveled, not the reading on the dial. This is the measurement of the shim pack without the bearing preload, which will be added later.
10. Remove the J 39704 .

Important: Do not remove the J 39704 from the differential.

11. Remove the differential from the housing.

Important: Removal of the spacers prevents the spacers from falling out during the installation of the pinion gear. Mark the spacers and indicate from which side you removed the spacers. Reassemble the spacers as removed in order to ensure that the shim pack measurement is correct.

12. Remove any spacers used in the procedure from the housing.