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Locking


The 1986-87 7-1/2 and 8-1/2 inch Eaton locking differential type drive axles incorporate a load limiting feature to reduce the chances of axle shaft damage under high torque engagement conditions. The number of tangs on the inner most disc of the lefthand clutch pack has been reduced, allowing these tangs to shear in the event of a high torque engagement of the locker. When the tangs shear, the lock mechanism is disengaged which limits the torque transmitted to the axle shafts.
If the load limiting disc shears, the differential will continue to operate as an open differential with some limited slip action of the clutch packs at low torques. No additional differential damage should occur while driving with a sheared load limiting disc. When the tangs shear, the metal is trapped by the splines of the cam plate, thus preventing further damage.
If locking differential will not lock, disassemble and inspect unit as described in overhaul procedures. If torque limiting disc is damaged, left hand clutch plates and wave spring replacement is necessary.


Fig. 7 Governor & Latch Bracket Bushing Removal.:




Fig. 8 Eaton locking differential exploded view. Models w/8-1/2 inch ring gear:





W/8-1/2 INCH RING GEAR

Case Disassembly

1. Note position of governor and latching bracket for assembly, then remove side bearings and ring gear as outlined for standard differentials.
2. Remove governor assembly and latching bracket by pulling retaining bushings from case, Fig. 7. Pull latching bracket spring aside when removing bushings to prevent damage.
3. Remove lock screw and pinion shaft, Fig. 8, then roll differential pinions to access window by turning side gears and remove pinions.
4. Remove pinion thrust washers and thrust block, keeping all components in order for assembly.
5. Remove right side gear, disc pack and shim assembly, and guide clips.
6. Remove left cam gear and disc pack assembly along with shim and guide clips.
7. Clean and inspect all components, keeping components in order for assembly.
8. Replace components that are damaged, deformed or excessively worn. Due to critical tolerances required for proper operation, the differential case cannot be serviced separately. If case is defective, the entire differential assembly must be replaced. In addition, internal clearances are such that shims, thrust block or gears should not be replaced unnecessarily, even if slight wear patterns are evident. If shims, thrust block or side gears must be replaced, measurement and replacement procedures must be performed as outlined in order to maintain critical assembly clearances.

Cam Gear Clutch Service

1. Remove retaining ring from end of cam gear, Fig. 8.
2. Remove discs and cam plate from gear, keeping all components in order.
3. Clean and inspect components, and replace any that are damaged, distorted or excessively worn. If cam gear must be replaced, refer to ``Cam Gear Shim Selection'' for shim selection procedures prior to case reassembly.
4. Position gear on flat surface with hub end up, and assemble cam plate onto gear with cam form down to mate with cam form on gear.
5. Assemble 2 eared discs, 1 splined disc and 1 wave washer on cam gear, starting with eared disc as shown in Fig. 8.
6. Alternately assemble 3 eared discs and 2 splined discs on cam gear hub, starting with eared discs.
7. Install retaining ring, ensuring that retainer is fully seated.

Side Gear (R.H.) Clutch Service

1. Remove disc pack and shim from side gear, keeping components in order.
2. Clean and inspect components, and replace any that are damaged, deformed or excessively worn. If side gear must be replaced, refer to ``Side Gear Shim Selection'' for shim selection prior to case assembly. If side gear hub is scored or worn, inspect bore in case and replace assembly if bore is damaged or worn.
3. Alternately assemble eared discs and splined discs on side gear hub, starting with eared disc as shown in Fig. 8.
4. Install original shim or replacement shim of same thickness if original side gear is being used.


Fig. 9 Differential pinion backlash measurement. Models w/Eaton locking differential & 8-1/2 inch ring gear:





Cam Gear Shim Selection

1. Install cam gear assembly in case using original thrust washer or washer of equal thickness.
2. Mount differential pinions and thrust washers in proper installed position in case, manually depress cam gear into bore and insert pinion shaft through case and pinion assemblies, and secure shaft with lockscrew. If pinion shaft cannot be inserted, it will be necessary to replace cam gear shim with one of less thickness.
3. Index one tooth of pinion gear nearest shaft lockscrew so that tooth points downward, perpendicular to case flange.
4. Wedge large tapered screwdriver between cam gear and pinion shaft to hold gear compressed in bore.
5. Mount suitable dial indicator on case with pointer bearing against indexed differential pinion tooth, Fig. 9.
6. Ensure that pinion is firmly pulled back in seat, then rock pinion back and forth, read backlash clearance from dial indicator and note reading.
7. Index tooth of opposite differential pinion as outlined in step 3, then repeat steps 5 and 6.
8. Replace cam gear assembly shim as needed to obtain differential pinion backlash of .010-.018 inch. If cam gear is replaced, perform ``Thrust Block Selection'' procedure during case assembly to ensure proper case assembly clearances.



Side Gear Shim Selection
When side gear is replaced, or if side gear shim is damaged and proper thickness must be determined, select proper side gear shim thickness by measuring backlash between side gear and differential pinions. Follow procedure outlined for ``Cam Gear Shim Selection,'' using fully assembled side gear properly installed in case and select a shim that will provide .002-.010 inch backlash between side gear and differential pinions.


Fig. 10 Side gear spread measurement. Models w/Eaton locking differential & 8-1/2 inch ring gear:





Thrust Block Selection
If cam gear and/or side gear have been replaced, or if it is necessary to replace thrust block and original dimension cannot be determined, use the following procedure during differential case assembly to determine proper thrust block dimension.
1. Install cam gear and side gear assemblies in respective positions in case, insert differential pinion shaft through case bores and secure with lock screw.
2. Wedge large tapered screwdrivers or equivalent tools between cam gear and pinion shaft and side gear and pinion shaft to seat gears in case.
3. Using suitable gauge, measure distance between face of cam gear and face of side gear, Fig. 10, and record reading. Ensure that gauge ends rest on gear faces, not gear teeth when measuring side gear spread.
4. Measure thickness of original thrust block at outer corner and record dimension.
5. Select thrust block with thickness zero to .006 inch less than side gear spread measured in step 3. If original thrust block is serviceable, but does not provide the specified zero to .006 inch clearance, righthand side gear can be reshimmed to provide proper thrust block clearance as long as side gear backlash is maintained within the specified .002-.010 inch.


Fig. 8 Eaton locking differential exploded view. Models w/8-1/2 inch ring gear:




Fig. 11 Governor & latching bracket installation. Eaton locking differential:





Differential Case Assembly

1. Install 4 clutch pack guide clips on cam gear clutch pack, using heavy grease to retain clips.
2. Install cam gear assembly along with shim in flange end of case, Fig. 8. If cam gear has been replaced, perform shim selection procedure prior to installation.
3. Install 4 guide clips on assembled sidegear clutch pack using grease to retain clips.
4. Install side gear assembly in case along with shim. If side gear has been replaced, perform shim selection procedure prior to installation.
5. Lock axle shaft in vise with sufficient portion of spline protruding from vise to engage side gear, then mount case assembly on axle and engage axle with side gear.
6. Install thrust washers on back of differential pinions using grease to adhere washers.
7. Install one pinion assembly through small case opening while simultaneously installing remaining pinion and thrust block through large opening.
8. Rotate assembly approximately 90° to position open side of thrust block toward small opening in case and pinions in proper installed position. If side gears and/or thrust block have been replaced, refer to ``Thrust Block Selection Procedure'' to ensure proper assembly clearances.
9. Insert pinion shaft ensuring that pinion thrust washers are properly positioned, then install new lock screw and torque screw to 20 ft. lbs.
10. Insert governor assembly and latching bracket into case, Fig. 11, positioning straight end of latching bracket spring over and to the outside of the engagement shaft to preload bracket against governor.
11. Press governor assembly bushing into case to a depth which will allow .004-.020 inch shaft endplay.
12. Press latching bracket bushing into case to a depth which will provide zero to .003 inch shaft end play.
13. Install ring gear and bearings as outlined for standard differentials. Always use new bolts of proper type when installing ring gear. Do not reuse old bolts.



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