Assembly

Fig. 18 Checking pinion depth:

Fig. 19 Pinion depth code:

Setting Pinion Depth

1. Install drive pinion front and rear outer races. On rear differentials use tool J-8092 with adapter J-24256 for front race and J-24252 for rear race. On front differential use tool J-29039 for front race and J-29038 for rear race.
2. Lubricate and install front and rear bearings to be used for final assembly into their respective races.
3. On rear differentials install gauging plate J-23597-7, preload stud and pilot J-23597-9 through front and rear bearings and tighten nut. On front differentials install gauging plate J-23597-26, preload stud and pilot J-23597-27 through rear bearing and J-23597-21 through front bearing and tighten nut.
4. Rotate bearings to assure proper seating, then tighten locknut to 20 inch lbs. for new bearings, or 8-10 inch lbs. for used bearings.
5. Place discs J-23597-8 for rear differentials or J-23597-6 for front differentials onto arbor J-23497-1, then place tool into side bearing bores and install bearing caps snugly.
6. Install dial indicator on arbor post, then preload dial indicator one half turn and tighten indicator in this position, Fig. 18.
7. Position dial indicator plunger on gauge plate and slowly move it across gauge plate until highest reading is obtained. Zero dial indicator on highest reading of gauge plate, Fig. 18.
8. Carefully swing plunger off gauge plate and note reading on dial indicator. Recheck to verify reading. The reading on the dial is the correct dimension for the rear pinion depth shim on a ``nominal'' pinion. Check drive pinion head markings. The pinion depth code which is in the lowest position of the three numbers, Fig. 19, indicates a necessary change in pinion mounting distance. A plus number indicates the need for a greater mounting distance (achieved by decreasing shim thickness). A minus number indicates the need for a smaller mounting distance (achieved by increasing shim thickness). If no pinion depth code is stamped on the head, the pinion is ``nominal.'' In this case, proceed to step 10.

Fig. 20 Pinion depth chart:

Fig. 21 Pinion depth chart:

9. Using chart in Fig. 20 or 21, determine proper shim variation to compensate for plus or minus markings. Shims are available in sizes ranging from .086-101 inch for rear differentials or .059-.077 inch for front differentials. An indicator reading of .001 inch requires shims of .100 and .101 inch respectively.
10. Place shim on drive pinion, then install rear bearing using an arbor press and tool J-6133. Do not press on roller cage. Press on inner race only.

Pinion Bearing Preload

1. Place drive pinion and collapsible spacer into carrier.
2. Lubricate and position front bearing to be used during final assembly into carrier, then install new oil seals.
3. Install companion flange on drive pinion, then apply hypoid lubricant to threads and install new pinion nut. On rear differentials, torque nut to 85 ft. lbs. On front differentials, torque nut to 125 ft. lbs.
4. Rotate drive pinion to insure bearings are fully seated, then wind 4-6 turns of string around pinion flange. Using a pull scale, check amount of pull required to rotate flange.
5. Continue to tighten pinion nut in small increments until required torque of 17 lbs. for new bearings, or 7-9 lbs. for used bearings is obtained. The pinion nut should be tightened only in small increments and the pull scale used after each tightening. Exceeding preload specifications will compress spacer too much and require replacement.

Fig. 22 Positioning pinion gears:

Fig. 23 Installing lockpin:

Fig. 24 Ring gear bolts tightening sequence. Rear differentials:

Fig. 25 Ring gear bolts tightening sequence. Front differentials:

Differential Case Reassembly

1. Install side gears and thrust washers in differential case.
2. Position pinion gears 180° apart, Fig. 22, then roll gears into position, making sure they are aligned, to allow installation of pinion shaft.
3. Place thrust block between pinion gears and drive pinion into place. Make sure the lockpin hole in the cross shaft lock aligns with hole in case.
4. Check backlash between differential gears and pinion gears. If backlash is greater than .003 inch, make necessary adjustments with thrust washers. Thrust washers are available in thicknesses of .041, .045, .049 and .053 inch. Increasing washer thickness will decrease backlash. Decreasing washer thickness will increase backlash.
5. Install cross shaft lockpin, Fig. 23, then caulk end to avoid loosening.
6. Clean ring gear bolts then apply Loctite to threaded portion of bolts. Install ring gear, then install and torque bolts to 80-87 ft. lbs. for rear differentials or 44-58 ft. lbs. for front differentials in sequence shown in Figs. 24 and 25.

Fig. 26 Checking side bearing clearance:

Fig. 27 Installing bearing shims:

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 J-24244 for first bearing, then support case on J-8107-2 and install opposite bearing. For front differentials use tools J-8092 and J-29036 for first bearing, then support case on tool J-8107-2 and install opposite bearing.
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. 26. Record thickness.
6. Determine proper shims for installation. A predetermined dimension of .002 inch is required for proper preload. Therefore, add .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.
8. Remove case from carrier, then carefully remove both side bearings. Install shims as determined in steps six and seven behind each bearing, Fig. 27, 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:

Fig. 29 Checking backlash:

10. Check ring gear runout, Fig. 28. If runout exceeds .002 inch, correct by cleaning or replacing parts as necessary.
11. Install dial indicator against ring gear teeth making sure indicator button is perpendicular with tooth travel, Fig. 29. 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.

Fig. 30 Gear tooth contact pattern:

Gear Tooth Contact Pattern

Prior to final assembly, a ``Gear Tooth Contact Pattern'' check is necessary to assure correct relationship between gear sets. Gear sets which are mispositioned may be noisy and have a short life. With a contact pattern check, the most desirable contact between ring gear and drive pinion can be assured.
1. Wipe oil out of carrier and carefully clean each ring gear tooth.
2. Apply marking compound to all ring gear teeth using a medium stiff brush. When properly used, the pinion tooth contact area will be visible when a hand load is applied.
3. Apply a hand load to companion flange and rotate ring gear one revolution in each direction. Excessive turning of ring gear is not recommended.
4. Observe pattern made on ring gear teeth and compare with Fig. 30. A correct contact pattern should be centrally located up and down on the face of the ring gear teeth.

Contact Pattern Adjustment

Backlash and position of drive pinion in differential carrier are the only two adjustments which can be made that will affect the contact pattern. The effects of bearing preload adjustments are not readily apparent with tooth pattern checks. However, these adjustments should be within specifications before proceeding with backlash and drive pinion adjustments.
The drive pinion position is adjusted by increasing or decreasing the shim thickness between the pinion head and inner race of rear bearing. Increasing the shim thickness will move the pinion closer to center line of ring gear. Decreasing shim thickness will move pinion farther away from center line of ring pinion.
Backlash is adjusted by means of the side bearing adjusting shims which moves the entire case and ring gear assembly closer to or further away from the drive pinion. To increase backlash, increase right shim and decrease left shim an equal amount. To decrease backlash, decrease right shim and increase left shim an equal amount.
It may be necessary to adjust both pinon depth and backlash to obtain the correct pattern.