Side Bearing Preload & Initial Backlash Setting

If original side bearings, differential case, ring gear and pinion and differential carrier are being used, and the pattern check taken prior to disassembly showed proper tooth contact, the original (or new shims of the same thickness) may be reinstalled in their original locations. If new side bearings are being installed, and the pattern check taken prior to disassembly showed proper tooth contact, the following alternate procedure of shim selection may be used.

1. Using a micrometer, measure new bearing thickness and compare with the old measurement.
2. If new bearing is thicker, subtract numerical difference between new and old bearing from shim pack.
3. If new bearing is thinner, add numerical difference between new and old bearing to original shim pack. If new bearings and/or differential case, ring and pinion or differential carrier are being installed, new shims must be selected for installation behind side bearings as follows.
4. Install side bearings to be used during final assembly on differential case. Do not install shims at this time. For rear differentials use tool No. J-24244 for first bearing, then support case on tool No. J-8107-2, or equivalents, and install opposite bearing. For front differentials use tool Nos. J-8092 and J-29036, or equivalents, for first bearing, then support case on tool No. J-8107-2, or equivalent, and install opposite bearing.

Fig. 26 Checking side bearing clearance:

5. Mount case into carrier bores, then move ring gear tight against ring gear side and away from pinion and hold in this position. Using a feeler gauge thick enough to produce a slight drag, measure clearance between bearing and differential carrier on side opposite ring gear, Fig. 25. Record thickness.
6. Determine proper shims for installation. A predetermined dimension of .002 inch is required for proper preload. Therefore, add 0.002 inch for proper preload to clearance measured in Step 5. This will provide the necessary combined total thickness of both shim packs.
7. Divide total dimension into two shim packs so numerical difference between packs equals numerical difference between the original shim packs.

Fig. 27 Installing bearing shims:

8. Remove case from carrier, then carefully remove both side bearings. Install shims as determined in steps six and seven behind each bearing, Fig. 26, and install bearings into case.
9. Install case onto carrier, tapping carefully into place, then install bearing caps into original locations and torque bolts to 75 ft. lbs. for rear differentials or 50 ft. lbs. for front differentials.

Fig. 28 Checking ring gear runout:

10. Check ring gear runout, Fig. 27. If runout exceeds .002 inch, correct by cleaning or replacing parts as necessary.

Fig. 29 Checking backlash:

11. Install dial indicator against ring gear teeth making sure indicator button is perpendicular with tooth travel, Fig. 28. If backlash is not within .005-007 inch for rear differentials or .004-006 inch for front differentials, the shims behind each side bearing must be adjusted. In order to maintain proper preload when backlash is adjusted, the total thickness of both shim packs must be adjusted. Therefore, if necessary to increase one shim pack, the opposite shim pack must be deceased an equal amount.
12. To increase backlash, increase right side bearing shim and decrease left side bearing shim. To decrease backlash, decrease right side bearing shim and increase left side bearing shim. Backlash changes approximately .002 inch for each .003 inch shim change.