Differential Rebuild - Rear

Complete disassembly, inspection, and rebuild of the rear differential including bearing races, pinion seal, carrier bearings, and gear pattern setup with proper shim selection and preload adjustment.

Warnings

Tools required

Parts

• Differential rebuild kit (bearings, races, seals, shims) × 1 — Use OEM specification for your axle ratio
• Pinion seal × 1 — GM 26052883 or equivalent
• Pinion nut × 1 — GM 11515669 or equivalent
• Pinion bearing spacer/crush sleeve × 1 — Included in rebuild kit
• Carrier bearing shims (assorted) × 1 — Use OEM specification
• Pinion depth shims (assorted) × 1 — Use OEM specification
• RTV silicone gasket maker (black) × 1 — GM 12378521 or equivalent
• Ring gear bolts (if reusing ring gear) × 10 — GM 11588765 or equivalent
• Differential cover gasket or RTV × 1 — Use RTV sealant
• Brake cleaner × 2 — Use as needed
• Shop towels × 1 — Use as needed

Fluids

• ACDelco 75W-90 Synthetic Gear Oil — 2.5 qt

Preparation

1. Park vehicle on level ground and engage parking brake
2. Loosen rear wheel lug nuts while vehicle is on ground
3. Raise rear of vehicle and support securely on jack stands at frame rails
4. Remove rear wheels
5. Place drain pan under differential
6. Mark driveshaft and pinion flange orientation for reinstallation alignment
7. Take photos of component positions before disassembly for reference
8. Ensure work area is clean and well-lit with adequate space for component layout

Procedure

1. 1

   Drain differential and remove cover
   Remove differential cover bolts in a crisscross pattern to prevent warping. Carefully pry cover loose and allow gear oil to drain completely into pan. Remove cover gasket material and clean mating surfaces thoroughly with scraper and brake cleaner. Inspect drained fluid for metal particles indicating wear.
   Torque spec

   Cover Bolts42 Nm (31 lb-ft)
2. 2

   Remove driveshaft
   Remove the four U-joint strap bolts at the differential pinion flange. Support driveshaft and slide it rearward out of transmission extension housing. Plug transmission to prevent fluid loss. Secure driveshaft clear of work area maintaining alignment marks visible.
   Torque spec

   Driveshaft U-Joint Straps20 Nm (15 lb-ft)
3. 3

   Mark and measure carrier bearing preload
   Using a dial indicator mounted on the housing, measure and record ring gear backlash at four points around the gear (should be 0.003-0.010 inch). Mark carrier bearing cap orientation with punch marks. Measure and record pinion rotating torque using inch-pound torque wrench (should be 15-35 in-lb for new bearings, 5-15 in-lb for used). Record all measurements for comparison during reassembly.
4. 4

   Remove carrier assembly
   Remove carrier bearing cap bolts and carefully lift caps off (they may be tight). Use pry bars to carefully lift carrier assembly with ring gear out of housing. Keep carrier bearing races, shims, and caps together and labeled left/right for reference. Place carrier assembly on clean workbench.
5. 5

   Remove pinion assembly
   Hold pinion flange with holding tool and remove pinion nut (discard - do not reuse). Use puller to remove pinion flange. Tap pinion shaft rearward out of housing using soft hammer. Remove pinion, crush sleeve, inner bearing, and shims as an assembly. Carefully collect and measure all pinion depth shims - record thickness for reference.
6. 6

   Remove bearing races from housing
   Using bearing race puller or brass drift, carefully remove pinion bearing races from front and rear of housing. Remove carrier bearing races from housing bores. Mark each race location and inspect for pitting, scoring, or wear. Clean all housing bores thoroughly with brake cleaner and inspect for damage.
7. 7

   Disassemble and inspect carrier
   If reusing ring gear: mark ring gear position on carrier, heat ring gear bolts with torch, and remove (discard bolts). Use bearing puller to remove carrier bearings from case. Remove differential pinion shaft lock bolt, pinion shaft, spider gears, and side gears. Inspect all components for wear, scoring, or damage. Check ring gear teeth and pinion for wear patterns, chips, or cracks. Replace worn components.
8. 8

   Install new bearing races
   Using hydraulic press and proper bearing race drivers, install new pinion bearing races into housing front and rear bores. Ensure races are seated completely and squarely - they should be 0.000-0.005 inch below housing face. Install new carrier bearing races into housing bores using same method. Verify proper seating with feeler gauge around entire circumference.
9. 9

   Determine pinion depth
   Install pinion depth gauge tool (GM J-21777-01) into housing with appropriate adapters for your gear set. Using dial indicator, measure pinion depth and compare to variance number etched on pinion head (+ or - number in hundredths). Calculate required shim pack thickness. Install calculated shim pack on pinion shaft behind rear bearing. Press rear pinion bearing onto shaft using hydraulic press and proper bearing driver.
10. 10

    Assemble and install pinion
    Install pinion with rear bearing and shims into housing. Install new crush sleeve, front pinion bearing, pinion seal (lubricate seal lip with gear oil), and pinion flange. Install new pinion nut and tighten gradually while checking rotating torque with inch-pound torque wrench. Target 15-25 in-lb rotating torque for new bearings. DO NOT back off nut - if overtightened, discard crush sleeve and start over with new one.
11. 11

    Reassemble differential carrier
    Lubricate all components with gear oil. Install side gears and spider gears into carrier with thrust washers. Install pinion shaft and new lock bolt (torque per rebuild kit specifications, typically 25-35 lb-ft). If installing ring gear: heat new bolts, apply threadlocker, install in crisscross pattern torquing to rebuild kit specifications (typically 70-90 lb-ft). Press new carrier bearings onto case using hydraulic press and bearing drivers.
12. 12

    Determine carrier bearing shim pack
    Install carrier assembly into housing without shims. Install bearing caps finger-tight in marked positions. Measure gap between bearing races and caps on both sides using feeler gauges. Add 0.010 inch to each side measurement for preload. This determines total shim pack needed for each side. Install shim packs and bearing caps.
13. 13

    Set ring gear backlash
    With carrier installed and caps torqued, mount dial indicator against ring gear tooth. Check backlash at four points - should be 0.003-0.010 inch, with variance no more than 0.002 inch around gear. If backlash is incorrect, transfer shims from one side to the other (adding to one side reduces backlash, adding to opposite side increases backlash). Recheck after each adjustment until backlash is within specification.
14. 14

    Check gear contact pattern
    Apply thin coat of gear marking compound to 8-10 ring gear teeth. Rotate pinion in both directions under light resistance (use strap wrench on flange) to create contact pattern. Check pattern on drive and coast sides. Pattern should be centered on tooth - adjust pinion depth shims if pattern is too high or low, adjust backlash if pattern is too far toward toe or heel. Repeat until pattern is correct. This may require removing and reshimming pinion.
15. 15

    Final assembly and fill
    Clean all gear marking compound off gears with brake cleaner. Apply thin bead of RTV silicone to differential housing cover mating surface. Install cover and torque bolts in crisscross pattern to specification. Wait 1 hour for RTV to cure. Remove fill plug and fill differential with ACDelco 75W-90 synthetic gear oil until oil reaches bottom of fill hole (approximately 2 quarts). Install fill plug with new washer. Reinstall driveshaft aligning marks made during removal. Torque U-joint strap bolts evenly in crisscross pattern. Install wheels and torque lug nuts in star pattern.
    Torque spec

    Cover Bolts42 Nm (31 lb-ft)

    Fill Plug51 Nm (38 lb-ft)

    Driveshaft U-Joint Straps20 Nm (15 lb-ft)

    Wheel Lug Nuts190 Nm (140 lb-ft)

Reassembly

1. Ensure all RTV sealant has cured for minimum 1 hour before filling with gear oil
2. Do not reuse crush sleeves, pinion nuts, ring gear bolts, or seals - these are single-use components
3. Verify driveshaft is installed with alignment marks matched to prevent vibration
4. Double-check all torque specifications have been met before test drive

Verification

• Lower vehicle and test drive 10-15 miles, listening for abnormal whine, growl, or clunking noises
• Check for gear oil leaks at pinion seal and differential cover after test drive
• Verify smooth engagement when accelerating and decelerating - no binding or chatter
• Re-check fluid level after test drive and top off if needed
• Normal break-in period is 500 miles - avoid heavy loads or trailer towing during this time
• Slight gear noise during first 50-100 miles is normal as gears seat - should diminish with use
• If whine increases with speed or persists beyond break-in, recheck backlash and gear pattern

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