Differential Rebuild - Rear

Complete disassembly, inspection, and rebuild of the rear differential assembly including bearing replacement, gear setup, and backlash adjustment for the AAM 11.5" rear axle.

Warnings

Tools required

Parts

• Differential rebuild kit (bearings, seals, shims) × 1 — Use OEM specification for AAM 11.5"
• Ring and pinion gear set (if worn or damaged) × 1 — Match existing gear ratio or desired ratio
• Pinion bearing shim kit × 1 — Use OEM specification
• Carrier bearing shim kit × 1 — Use OEM specification
• Pinion seal × 1 — Use OEM specification
• Differential cover gasket or RTV sealant × 1 — Mopar or equivalent
• Pinion nut × 1 — Use new OEM pinion nut
• Ring gear bolts (if reusing ring gear) × 1 — Use OEM specification
• Crush sleeve (if applicable to pinion setup) × 1 — Use OEM specification
• Gear marking compound × 1 — Standard differential marking compound
• Limited slip additive (if equipped with limited slip) × 1 — Mopar limited slip additive
• Thread locker (medium strength) × 1 — Loctite 242 or equivalent
• Brake cleaner or degreaser × 2 — Standard automotive brake cleaner

Fluids

• 75W-90 synthetic gear oil — 5.5 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Chock front wheels securely
3. Raise rear of vehicle and support with heavy-duty jack stands under frame rails
4. Remove both rear wheels
5. Place drain pan under differential
6. Verify you have all necessary specialty tools before beginning, particularly dial indicator, pinion depth gauge, and side bearing adjusting tool
7. If vehicle has been driven, allow differential to cool for at least 30 minutes
8. Take reference photos of driveshaft orientation and any shim locations

Procedure

1. 1

   Drain differential fluid and remove cover
   Remove differential cover fill plug to vent, then remove all cover bolts. Carefully pry cover loose and allow fluid to drain completely into drain pan. Remove cover and gasket material. Inspect fluid for metal particles or unusual debris which may indicate gear damage. Clean cover thoroughly and inspect for cracks.
2. 2

   Mark and remove driveshaft
   Mark driveshaft flange and pinion flange with paint or punch marks for proper alignment during reassembly. Remove the driveshaft U-joint retaining hardware (straps/U-bolts or flange bolts as equipped) at the pinion flange, noting the fastener type and count for reassembly. Support driveshaft and remove from vehicle. Install pinion flange cover or tape over pinion to prevent contamination.
3. 3

   Remove axle shafts and backing plates
   For the full-floating AAM 11.5" axle, the axle shafts can be removed independently of the brakes. Remove the axle shaft flange bolts at the wheel hub, then slide both full-floating axle shafts straight out of the axle tubes by hand (no slide hammer required on the full-float AAM 11.5" axle). Brake components need only be removed if servicing the hub/bearing assemblies. Remove backing plate mounting bolts and suspend backing plates out of the way without disconnecting brake lines. Be careful not to damage axle seals during removal.
4. 4

   Check and record initial gear settings
   Before disassembly, measure and record ring gear backlash using dial indicator mounted on carrier housing. Check pinion bearing preload by measuring rotational torque with inch-pound torque wrench on pinion nut (should feel drag, typically 15-35 inch-pounds for used bearings). Record these values for reference. Inspect gear tooth contact pattern by applying marking compound to several ring gear teeth, rotating gear through mesh, and examining pattern.
5. 5

   Remove differential carrier assembly
   For AAM 11.5" axle with adjustable carrier bearings, mark bearing cap orientation and loosen adjuster locks. Remove bearing cap bolts and bearing caps. Carefully thread back adjusters evenly to release preload on carrier bearings. Using pry bars, carefully work carrier assembly out of housing. Place carrier on clean work surface. Keep left and right bearing adjusters with their respective caps for reference.
6. 6

   Disassemble carrier and remove ring gear
   Remove ring gear bolts (standard right-hand thread on the AAM 11.5"). If bolts are tight, use penetrating oil and allow to soak. Tap ring gear with soft hammer to separate from carrier. Mark carrier case halves for proper reassembly orientation. Remove carrier case bolts and separate halves. Remove differential side gears, pinion gears, thrust washers, and spider gear assembly. Inspect all components for wear, scoring, or damage. Keep all components organized.
7. 7

   Remove pinion assembly
   Using pinion holding tool to prevent rotation, remove pinion nut. Mark pinion nut position and count exposed threads for reference. Remove pinion flange using puller if necessary. Remove pinion seal. Carefully tap pinion shaft out through rear of housing, catching pinion and bearings. Note direction and position of crush sleeve or shims. Remove outer pinion bearing from housing. Use brass drift to carefully drive out inner and outer pinion bearing races.
8. 8

   Remove carrier bearings and inspect all components
   Using bearing puller or press, remove carrier bearings from carrier housing. Keep bearings and races together if reusing. Remove carrier bearing races from housing using race driver. Clean all components thoroughly with solvent. Inspect ring and pinion teeth for wear patterns, scoring, pitting, or chipping. Inspect all bearing races and rollers for pitting, scoring, or discoloration. Check carrier housing for cracks or damage. Inspect spider gears and side gears for excessive wear. Replace any worn or damaged components.
9. 9

   Install new pinion bearing races and determine pinion depth
   Using race driver and press or hammer, install new inner and outer pinion bearing races squarely into housing. Races must be fully seated. Use pinion depth gauge tool set per manufacturer instructions to determine correct shim thickness for proper pinion depth. This is critical for correct gear tooth contact. Install selected shim(s) on pinion shaft. Install inner pinion bearing onto pinion shaft using press. Verify pinion gear depth marking (etched on pinion face) and compare to ring gear marking to determine if additional shim adjustment is needed.
10. 10

    Install pinion assembly and set preload
    Install new crush sleeve (or solid spacer with shims depending on design) onto pinion shaft. Lubricate outer pinion bearing with gear oil and install into race. Carefully insert pinion assembly through housing from rear, guiding through bearings. Install pinion flange and new pinion nut. Using pinion holding tool, tighten pinion nut gradually while checking preload with inch-pound torque wrench. Target preload is typically 20-40 inch-pounds for new bearings, 10-20 inch-pounds over original preload for used bearings. Tighten in small increments as crush sleeve compresses - DO NOT overtighten as crush sleeve cannot be reused if compressed too far.
11. 11

    Assemble differential carrier with new bearings
    Press new carrier bearings onto carrier housing using appropriate bearing driver. Ensure bearings are fully seated against carrier shoulders. Reassemble differential internals: install spider gear assembly, side gears, and thrust washers into carrier case halves. Align case halves using alignment marks and install case bolts with thread locker. Clean ring gear mating surface on carrier thoroughly. Heat ring gear in hot water (150-180°F) to expand for easier installation. Install ring gear onto carrier, align bolt holes, and install new ring gear bolts with thread locker. Tighten bolts in star pattern progressively.
12. 12

    Install carrier assembly and set bearing preload
    Lubricate carrier bearings with gear oil. Install carrier assembly into housing. Install bearing caps in correct orientation per marks made during disassembly. Install adjuster locks loosely. Thread in bearing adjusters evenly on both sides until carrier is centered and bearings contact races. Continue adjusting to achieve zero backlash. Back off one adjuster slightly, then tighten opposite adjuster while checking carrier endplay with dial indicator. Adjust until endplay is zero, then tighten both adjusters evenly 1-2 notches beyond zero for proper bearing preload.
13. 13

    Set ring gear backlash
    Mount dial indicator against ring gear tooth at 90 degrees to gear face. Rock ring gear back and forth while holding pinion stationary and measure backlash. Target backlash is typically 0.005-0.009 inches (verify with ring and pinion manufacturer specifications). Adjust by loosening one adjuster and tightening opposite adjuster by same amount to move ring gear closer to or farther from pinion. Recheck preload after each adjustment. Check backlash at 4 points around ring gear (90-degree intervals) - variation should not exceed 0.002 inches.
14. 14

    Check gear tooth contact pattern
    Apply thin, even coating of gear marking compound to 8-10 ring gear teeth. Rotate pinion in both directions under light resistance to transfer pattern. Examine contact pattern on ring gear teeth - proper pattern should be centered on tooth face, slightly toward toe, covering 50-60% of tooth surface. Adjust pinion depth (shims) if pattern is too high or low on tooth. Adjust backlash if pattern is too far toward toe or heel. Repeat marking and adjustment until proper pattern is achieved in both drive and coast directions.
15. 15

    Final assembly and fluid fill
    Once gear pattern is correct, tighten bearing cap bolts and adjuster locks securely. Install new pinion seal using seal driver, ensuring seal is square and seated to proper depth. Clean differential cover and housing mating surfaces thoroughly. Apply RTV silicone sealant or install new gasket per manufacturer specifications. Install cover and tighten bolts in star pattern. Install axle shafts with new seals if needed. Reinstall backing plates, brakes, and wheels. Fill differential with approximately 3.5-4.0 quarts of 75W-90 synthetic gear oil to the bottom of the fill plug opening (verify exact Mopar fill spec for the AAM 11.5"). Add limited slip additive if equipped with limited slip differential. Install fill plug. Reinstall driveshaft aligned with original marks. Lower vehicle.

Reassembly

1. Ring gear bolts must be tightened in star pattern to proper specification with thread locker applied
2. Bearing adjusters must be tightened evenly to prevent carrier from binding or cocking in housing
3. Pinion preload cannot be reduced once crush sleeve is compressed - if overtightened, crush sleeve must be replaced and process restarted
4. Backlash must be verified at multiple points around ring gear to ensure carrier is properly centered
5. Driveshaft must be installed in original orientation to maintain balance
6. Allow RTV sealant to cure per manufacturer instructions before filling with fluid if used instead of gasket

Verification

• Verify no fluid leaks from pinion seal, cover gasket, or axle seals after initial fill
• Rotate pinion by hand - should turn smoothly with consistent drag from bearing preload, no tight spots or excessive play
• Verify final backlash is within 0.005-0.009 inches and does not vary more than 0.002 inches around ring gear
• Verify pinion rotating torque is within specification (typically 20-40 inch-pounds for new bearings)
• Test drive vehicle at various speeds, listening for gear whine, howling, or clunking which would indicate improper setup
• After 50-100 miles, recheck fluid level and inspect for leaks
• After 500 miles, drain and replace gear oil to remove any break-in debris, then recheck fluid level

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