Special tools are required throughout the following procedures. If the tools are not on hand, or obtainable, do not attempt overhauling the differential. If is not necessary to remove the complete axle assembly from the vehicle for differential service.
See Figures 1, 2 and 3
- Raise and safely support the rear of the vehicle on the frame rails in front of rear spring. This will allow the axle assembly to hang free for more working room. Remove the axles and driveshaft. Thoroughly clean the outer area of the housing and axle tubes with a safe cleaning solvent and wipe dry.
- Place a drain pan under the differential. Remove the cover and drain the lubricant.
- If equipped with a Sure-Grip differential do not perform this step. Wash and flush the internal components of the differential. Allow them to dry.
- Side play and run-out checks should be made at this time. They will be very useful in reassembly.
- To measure for side play: Position a small pry bar between the left side of the axle housing and case flange. Use a prying motion to determine if any side play exists. There should be no side play.
- Side play resulting from bearing races being loose on the case hub requires replacement of the differential case. Otherwise, use the threaded adjuster to remove the side play before measuring the ring gear run-out.
- Eliminate any side play. Attach a dial indicator to a pilot stud. Place the indicator at a right angle to the brake exiciter ring or ring gear. The plunger should exert a slight pressure. Zero the dial.
- Rotate the ring gear several revolutions. Observe the dial indicator pointer. Mark the differential case and ring gear at the maximum run-out. Run-out should not exceed 0.005 in. (0.127mm). If run-out exceeds 0.005 in. (0.127mm) a damaged differential case could be the cause. The marking of the ring gear and differential case will be used for references later on.
- Remove the Rear Wheel Anti-Lock (RWAL) sensor, if equipped.
- Marking the housing and differential case bearing caps for installation reference.
- Remove the threaded bearing adjuster lock from each bearing cap. Loosen, but do not remove the bearing caps.
- Insert the special wrench C-4164, or equivalent, through the axle tube and loosen the threaded bearing adjusters on each side. Use extreme caution to avoid damage to the RWAL brake exciter ring, if equipped.
- Remove the bearing caps, adjusters and the differential case assembly. Each differential bearing cup and threaded adjuster must be kept with their respective bearing. They are a matched set.
- Use an inch pound torque wrench to measure the pinion gear preload. Rotate the pinion yoke with the torque wrench and record the maximum amount of torque necessary. Remove the pinion yoke.
- Remove the pinion seal. Force the pinion shaft out of the front bearing and remove the bearing cup. They must be replaced at assembly time. Discard the collapsible spacer.
- Use the appropriate puller and remove the pinion front and rear bearing cups. Remove the pinion gear depth shims. Keep the shims together.
- Press the rear pinion bearing from the shaft.
- Do not remove the ring gear from the case unless gear replacement or flange run-out must be measured.
- To measure flange run-out: If the ring rear run-out exceeds 0.005 in. (0.127 mm) the case flange run-out should be checked. Clamp the case assembly in a soft jawed vise. Remove the ring gear mounting bolts. The bolts have LEFT-HAND threads. Remove the ring gear using a hammer and brass drift.
- Detach the RWAL brake exiciter, if equipped, with a brass drift.
- Install the case into the housing with the bearing cups and threaded adjusters to their original positions.
- Install the bearing caps and bolts. Use the special wrench to tighten both adjusters to their original positions.
- Mount a dial indicator and position the plunger against the right side of the case flange between the outer edge and bolts holes. Zero the indicator.
- Rotate the case several times. Mark the area of maximum run-out. The flange run-out should not exceed 0.003 in. (0.076mm). If the run-out exceeds 0.003 in. (0.076mm), the differential case must be replaced.
- It is possible to reduce the combined ring gear/flange run-out by positioning the marked area of maximum run-out 180° opposite the other marked maximum area.
- Remove the differential case from the axle housing.
- Clamp the case assembly in a soft jawed vise.
- Remove the pinion gear mate shaft lock screw and the shaft. Rotate the differential side gears until the differential pinion gears are located at a case opening and remove them.
- Remove the differential side gears and thrust washers.
- Remove the case from the vise. Press off the carrier side bearings.
- Clean all of the components in a safe solvent and allow them to dry. Inspect all components and replace as necessary. Inspect the RWAL brake exciter ring, if equipped, for damaged or broken teeth. Replace it if necessary.
Exciter Ring Replacement
If installed, the ring gear must be removed before the RWAL brake exciter can be replaced.
- If RWAL brake exciter ring replacement is necessary, remove with a hammer and drift.
- Heat the replacement exciter ring with a heat lamp or by immersing in a hot fluid. The temperature should not exceed (149°C) 300°F. Do not use a torch to heat the ring.
- After heating, quickly position the exciter ring on the differential case adjacent to the flange.
Differential Case Assembly
- Lubricate all the differential case components with gear lubricant. Place the thrust washers on the differential side gears. Position the gears in the differential case counterbores.
If replacement side gears or thrust washers are used, refer to Side Gear Clearance Measurement and Adjustment.
- Position the thrust washers on the differential pinion gears. Mesh the pinion gears with the side gears. Ensure the pinion gears are exactly 180° opposite each other. Rotate the side gears to align the pinion gears and thrust washers. Align these components with the mate shaft bores in the case.
- Install the lock screw and tighten it with 90 inch lbs. (10 Nm). If the ring gear was removed, clean all contact surfaces.
- Use an Arkansas stone to remove any sharp areas from the chamfered inside diameter. If removed, install the exiciter ring.
- Heat the ring gear with a heat lamp or by immersing in a hot fluid. The temperature should not exceed (149°C) 300°F. Do not use a torch to heat the ring.
- Position the heated gear onto the case adjacent to the exiciter ring. Use three equally space pilot studs to align the gear with the flange holes.
- Insert new ring gear bolts (with left hand threads) through the differential case flange and thread them into the ring gear. Alternately tighten each bolt to 70 ft. lbs. (95 Nm).
- Place a differential bearing on each hub (bearing taper facing outward). Carefully seat the bearings on the hubs. An arbor press should be used with the installation tools. When installing a differential bearing, never apply force to the bearing cage because bearing damage will result.
Pinion Gear Assembly/Installation
- Select the correct pinion gear adjustment gauges. On 8 3 / 8 axles, use Tool Set C-3715-B or C-758-D6 for 9 1 / 4 axles (or equivalents).
- Insert both bearing cups into the differential housing bores. On 8 3 / 8 in. diameter, position Locating Spacer SP 6030 over the shaft of SP-5385 and follow it with the rear bearing. Position the tools (with bearing) in the differential housing. Install Shaft Locating Sleeve SP-5382. Install the pinion front bearing. Install Washer SP-6022 followed by Compression Sleeve SP-3194-B. Install Centralizing Washer SP-534 followed by Compression Nut SP-3193.
- On 9 1 / 4 in. diameter, position Locating Spacer SP-6017 over the shaft of SP 526 and follow it with the pinion rear bearing. Position the tools (with the bearing) in the differential housing. Install Shaft Locating Sleeve SP-1730. Install the pinion front bearing. Install Washer SP-6022 followed by Compression Sleeve SP-535-A. Install Centralizing Washer SP-534 followed by Compression Nut SP-533.
- Prevent compression sleeve tool from turning with Wrench C-3281, or equivalent. Tighten the nut to seat the pinion bearing cups in the housing. Allow the sleeve to turn several times during the tightening to prevent brinelling the bearing cups or the bearings.
Depth Shim(s) are positioned between the pinion gear rear bearing and pinion gear to provide separation distance. The required thickness of the depth shim(s) is determined according to the following information.
- Loosen the compression nut tool. Lubricate the pinion gear front and rear bearings with gear lubricant. Tighten the compression nut tool to 15-25 inch lbs. (1-3 Nm). Rotate the pinion gear several complete revolutions to align the bearing rollers.
- On 8 3 / 8 in. diameter ring gear axles: Install Gauge Block SP-5383 at the end of SP-526. Install Cap Screw SP-536. Tighten securely with Wrench SP-531.
- On 9 1 / 4 in. diameter ring gear axles: Install Gauge Block SP-6020 at the end of SP-526. Install Cap Screw SP-536. Tighten securely with Wrench SP-531.
- On 8 3 / 8 in. axles, position Crossbore Arbor SP-6029 in the differential housing.
- On 9 1 / 4 in. axles, position Crossbore Arbor SP-6018 in the differential housing.
- Center the tool. Place a piece of 0.002 in. (0.05mm) shim stock at each end of the arbor tool. Position the bearing caps on the arbor tool. Install the attaching bolts. Tighten the cap bolts to 10 ft. lbs. (14 Nm).
- Trial fit depth shim(s) between the crossbore arbor tool and gauge block tool. The depth shim(s) fit must be snug but not tight (drag friction of a feeler gauge blade). Depth shims are available in 0.001 in. (0.025mm) increments from 0.020 in. (0.5mm) 0.038 in. (0.96mm).
- Note the etched number on the face of the drive pinion gear (for example, -0, -1, -2, +1, +2, etc.). The numbers represent thousandths of an inch deviation from the standard. If the number is negative (-), add that value to the required thickness of the depth shims(s). If the number is positive (+), subtract that value from the thickness of the depth shim(s). If the number is 0, no change is necessary.
- Remove the tools from the differential housing.
- Position the depth shim selected above on the pinion shaft followed by the rear bearing (ensure the Contact surface, bearing and depth shim are clean and without foreign particles). Use Bearing Installer C-4040, or equivalent, for 8 3 / 8 in. diameter. Use Sleeve C-3095-A, or equivalent, for 9 1 / 4 in. diameter ring gear axles. Force the rear bearing onto the pinion shaft. An arbor press can be used with the installation tool.
- Lubricate the pinion gear front and rear bearings with gear lubricant. Install the pinion with rear bearings in the housing. Position the bearing replacement collapsible spacer at the end of the pinion gear. Position the pinion gear front bearing at the end of the pinion gear.
- Install the yoke. On 8 3 / 8 in. diameter use Installer C-3718 and Wrench C-3281. On 9 1 / 4 in. diameter use Installer C-496 and Wrench C-3281.
Because of the front bearing interference fit on the drive pinion gear shaft, it is necessary to use the tools to correctly seat the front bearing on the drive pinion gear shaft. Use care to prevent collapsing preload spacer during installation of the yoke and seating the front bearing.
- Remove the yoke and tools from the pinion gear. Install the pinion seal with Seal Installer. On 8 3 / 8 in. diameter use Installer C-4076, or equivalent. On 9 1 / 4 in. diameter use Installer C-3980 or C-4109, or equivalent. The seal is correctly installed when the seal flange contact the face of the differential housing flange. The outer perimeter of the seal is pre-coated with a special sealant. An additional application of sealant is not required.
- Install the yoke. Remove the tools. Install the Belleville washer. The convex side of the washer must face outward. Install the pinion nut.
- Hold the pinion yoke with Wrench C-3281, or equivalent. Initially tighten the drive pinion gear shaft nut enough to remove the bearing end-play. While tightening, rotate the pinion shaft to ensure the bearing rollers are correctly seated.
- Tighten the pinion nut to a minimum torque figure of 210 ft. lbs. (285 Nm).
- Remove the tools from the shaft. Rotate the pinion several complete revolutions (both directions) to additionally seat the bearing rollers. Never loosen the pinion gear nut to decrease the pinion gear bearing preload torque. If the specified preload torque is exceeded, a replacement collapsible spacer must be installed. The torque sequence will have to be repeated.
- Measure the bearing preload torque by rotating pinion gear with a Newton-meter or an inch pound torque wrench. The correct replacement bearing preload torque is 20-35 inch lbs. (2-4 Nm) for both 8 3 / 8 and 9 1 / 4 in. axles. Tighten the pinion gear nut a minimum of 210 ft. lbs. (285 Nm).
- When using the original pinion rear bearing and a replacement front bearing: The correct preload torque is 10 inch lbs. (1 Nm) in addition to the torque measured and recorded during disassembly. The bearing preload torque should be constant during a complete revolution of the drive pinion gear shaft. If the preload torque varies during rotation of the shaft, there is an internal binding that must be corrected before final assembly.
- If the specified torque is not obtained with 210 ft. lbs. (285 Nm), continue tightening the nut in small increments until the recorded bearing preload torque is obtained. The differential will be unacceptable for use if the final nut torque is less than 210 ft. lbs. (285 Nm). If the preload torque is not within the specified range this is also unacceptable.
Differential Case Installation
- Apply a coating of hypoid gear lubricant to the differential bearings, bearing cups and the threaded adjusters. Carefully position the assembled differential case in the housing.
- Observe the reference marks and install the differential bearing caps at their original locations
- Install the bearing cap bolts. Tighten the upper bolts to 10 ft. lbs. (14 Nm). Tighten the lower bolts finger-tight until the bolt head is lightly seated.
Bearing Preload Torque and Ring Gear Backlash Adjustment
The following limitations must be considered when adjusting the differential bearing preload torque and ring gear backlash. The maximum permissible ring gear backlash variation is 0.003 in. (0.076mm). For example, if the minimum backlash is 0.006 in. (0.152mm) at one location, the maximum can be no more than 0.009 in. (0.229mm) at another location.
This variation represents the maximum permissible run-out and it is important to mark the gears so the same teeth are engaged (meshed) during all backlash measurements. It is also important to maintain the specified threaded-adjuster torque while adjusting the differential bearing preload torque and the ring gear backlash. Excessive adjuster torque will introduce a high bearing load and cause premature bearing failure. Insufficient adjuster torque can result in excessive differential case free-play and ring gear noise.
The differential bearing cups will not always immediately follow the threaded adjusters as they are moved during adjustment. Ensure accurate bearing cup responses to the adjustments. Maintain the gear teeth engaged (meshed) as marked. The bearings must be seated by rapidly rotating the pinion gear a half turn back and forth. Do this five to ten times each time the threaded adjusters are adjusted.
- Use Wrench C-4164, or equivalent, to adjust each threaded adjuster inward until the differential bearing free-play is eliminated. Allow some ring gear backlash (approximately 0.01 in. or 0.25mm) between the ring and pinion gear. Seat the bearing cups with the procedure described previously.
- Install Dial Indicator C-3339, or equivalent. Position the plunger against the drive side of a ring gear tooth. Measure the backlash at 4 positions around the perimeter of the ring gear (with an arc interval of approximately 90° between each position) to locate the area of minimum backlash.
- Rotate the ring gear to the position of the least backlash (as indicated by the dial indicator pointer). Mark the gear so that all future backlash measurements will be taken with the same gear teeth meshed.
- Loosen the right-side, tighten the left-side threaded adjuster. Obtain backlash of 0.003-0.004 (0.076-0.102mm) with each adjuster tightened to 10 ft. lbs. (14 Nm). Seat the bearing cups with the procedure described previously.
- Tighten the differential bearing cap bolts. On 8 3 / 8 in. diameter to 70 ft. lbs. (95 Nm). On 9 1 / 4 in. diameter with 100 ft. lbs. (136 Nm).
- Use Wrench C-4164, or equivalent, to tighten the right-side threaded adjuster to 75 ft. lbs. (102 Nm). Seat the bearing rollers as previously described. Continue to tighten the right-side adjuster and seat bearing rollers until the torque remains constant at 75 ft. lbs. (102 Nm).
- Measure the ring gear backlash. If the backlash is not 0.006-0.008 in. (0.15-0.20 mm), continue increasing the torque at the right-side adjuster until obtained. Continue increasing the torque at the right-side threaded adjuster (seat the bearing cups with the procedure described above) until the specified backlash is obtained.
If all the instructions have been correctly completed, the left-side threaded adjuster should be approximately 75 ft. lbs. (102 Nm). If the torque is substantially less, the complete procedure must be completed.
- Tighten the left-side threaded adjuster until 75 ft. lbs. (102 Nm) is indicated. Seat the bearing rollers with the procedure previously described. Do this until the torque remains constant.
- After the adjustments are completed, install the threaded adjuster locks. On 9 1 / 4 in. diameter, the lock teeth are engaged with the the adjuster threads. On 8 3 / 8 in. diameter, the lock finger is engaged with an adjuster hole. Tighten the lock screws to 90 inch lbs. (10 Nm).
Side Gear Clearance Measurement and Adjustment
- The correct differential side gear clearance is obtained by selection of a thrust washer that has the correct thickness. Refer to the replacements parts catalog for the required side gear thrust washer package. When measuring side gear clearance, check each gear independently. One side gear can have an acceptable clearance and the other gear can have an unacceptable clearance. If it is necessary to replace a side gear, replace both gears as a matched set.
- Install the axle shafts and C-clip locks.
- Measure each side gear clearance. Insert a matched pair of feeler gauge blades between the gear and dif