Differential Rebuild - Rear

Complete disassembly, inspection, and rebuild of the rear differential assembly including bearing replacement, gear setup, and backlash adjustment.

Warnings

Tools required

Parts

• Rear differential rebuild kit (bearings, seals, shims) × 1 — Use OEM specification
• Pinion seal × 1 — Use OEM specification
• Pinion nut × 1 — Use OEM specification
• Ring and pinion gear set (if worn) × 1 — Match gear ratio to vehicle
• Differential cover gasket or RTV sealant × 1 — Motorcraft TA-357
• Drain plug washer × 1 — Use OEM specification
• Pinion bearing preload shims × 1 — Assortment for adjustment
• Carrier bearing shims × 1 — Assortment for adjustment

Fluids

• Motorcraft 75W-140 Synthetic Gear Oil — 2.5 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Chock front wheels securely
3. Raise rear of vehicle and support on jack stands at frame rails
4. Remove rear wheels using star pattern
5. Place drain pan under differential
6. Allow differential to cool completely if vehicle was recently operated
7. Take reference photos of driveshaft orientation and differential assembly
8. Clean exterior of differential housing thoroughly

Procedure

1. 1

   Drain differential fluid
   Remove the drain plug from the bottom of the differential housing using appropriate socket. Allow all gear oil to drain completely into drain pan. Inspect drained fluid for metal particles or debris indicating wear. Remove fill plug to aid drainage. Once drained, reinstall drain plug with new washer.
   Torque spec

   Drain Plug47 Nm (35 lb-ft)

   Fill Plug47 Nm (35 lb-ft)
2. 2

   Remove driveshaft
   Mark the driveshaft flange and pinion flange orientation with paint marker for proper reinstallation. Remove the four driveshaft bolts connecting the driveshaft to the differential pinion flange. Support the driveshaft and carefully lower it, then secure it to the frame with mechanics wire to prevent damage to the center support bearing.
   Torque spec

   Driveshaft Bolts85 Nm (63 lb-ft)
3. 3

   Remove differential cover
   Remove all differential cover bolts in a crisscross pattern to prevent warping. Carefully pry cover away from housing using plastic scraper at the pry points. Remove cover and gasket material. Inspect internal components for wear, scoring, or damage. Take photos of gear tooth contact pattern if possible. Clean all old RTV sealant from both cover and housing mating surfaces using plastic scraper.
   Torque spec

   Cover Bolts39 Nm (29 lb-ft)
4. 4

   Mark and remove carrier bearing caps
   Using a punch or marker, clearly mark the carrier bearing caps and housing for correct reinstallation position. Remove the carrier bearing cap bolts. Carefully remove both carrier bearing caps, keeping them organized with their respective bolts. Note the position and thickness of any shims behind the carrier bearings.
   ℹ️Carrier bearing caps are machined as matched pairs to the housing and are not interchangeable side-to-side.
5. 5

   Remove carrier assembly
   Carefully pry the carrier assembly out of the housing using pry bars on both sides simultaneously. Remove the carrier assembly with ring gear attached. Remove and keep all carrier bearing shims, labeling them for their respective sides (left/right) and measuring their thickness with micrometer. Record all measurements for reference during reassembly.
   ⚠The carrier assembly is heavy. Use proper lifting technique or have an assistant help remove it from the housing.
6. 6

   Remove pinion assembly
   Using the pinion holding tool to prevent rotation, remove the pinion nut. Mark the pinion shaft depth position relative to the housing before removal. Carefully tap the pinion shaft out of the housing from the rear using a soft-face hammer. Remove the pinion with front bearing, collapsible spacer, and oil seal as an assembly. Remove the rear pinion bearing from the housing using appropriate bearing puller.
   ℹ️The pinion nut is a one-time-use torque-prevailing nut and must be replaced. Do not reuse the old pinion nut.
7. 7

   Disassemble and inspect carrier
   Remove the ring gear bolts and separate the ring gear from the carrier. Inspect ring gear teeth for wear, scoring, pitting, or chipping. Drive out the differential pinion shaft lock pin. Remove the pinion shaft, side gears, pinion gears, and thrust washers. Press off the carrier bearings using hydraulic press, keeping left and right bearings separate. Inspect all components for wear and replace as necessary per rebuild kit.
   ℹ️Inspect ring gear bolt holes for thread damage. Clean and chase threads if necessary before reassembly.
8. 8

   Clean and inspect housing
   Thoroughly clean the differential housing interior with solvent and compressed air. Inspect housing for cracks, especially around bearing bores and mounting points. Remove old bearing races from the housing using race driver and hammer. Inspect pinion bearing bores for wear or scoring. Clean and inspect all threaded holes.
   ⚠Wear safety glasses when using compressed air. Ensure no debris or cleaning solvent remains in the housing.
9. 9

   Install new pinion bearings and races
   Install new pinion bearing races into the housing using bearing race driver, ensuring they are fully seated. Install the rear pinion bearing onto the pinion shaft using hydraulic press. Install the front pinion bearing onto the pinion shaft. Install the appropriate shim pack onto the pinion shaft based on the numbers marked on the new pinion head (typically +/- markings indicating variance from nominal).
   ℹ️Pinion depth is critical for proper gear contact. Use the variance marking on the pinion head to calculate required shim thickness.
10. 10

    Set pinion depth and preload
    Install the pinion assembly into the housing with the calculated shim pack. Install new collapsible spacer and pinion seal. Apply small amount of gear oil to pinion seal lips. Install pinion flange and new pinion nut. Tighten pinion nut gradually while checking rotating torque with inch-pound torque wrench. Target pinion bearing preload is 16-29 inch-pounds for new bearings. Do not over-tighten as collapsible spacer cannot be reused if compressed too much.
    ⚠If pinion nut is over-tightened, the collapsible spacer must be replaced and the process repeated. Tighten incrementally and check preload frequently.
11. 11

    Reassemble carrier assembly
    Install new carrier bearings onto the carrier using hydraulic press or bearing driver. Install side gears and pinion gears with thrust washers into the carrier, ensuring proper orientation. Install the pinion shaft through the carrier and gears. Align the lock pin hole and install new lock pin. Clean ring gear and carrier mating surfaces thoroughly. Heat ring gear to 250°F (121°C) if required to ease installation. Install ring gear onto carrier and install new ring gear bolts with thread locker. Torque ring gear bolts to specification in a star pattern.
    ⚠If heating ring gear, use proper heating equipment (oven or induction heater), not a torch. Uneven heating can warp the gear.
12. 12

    Install carrier and set backlash
    Install the carrier assembly into the housing with equal thickness shims on both sides as a starting point. Install carrier bearing caps in their marked positions. Tighten bearing cap bolts to secure assembly. Mount dial indicator on the housing with the plunger contacting a ring gear tooth at 90 degrees to the tooth face. Rock the ring gear back and forth while holding the pinion stationary. Measure backlash at 4 points around the ring gear. Target backlash is 0.13-0.20mm (0.005-0.008 inches). Adjust by moving shims from one side to the other (maintaining constant total shim thickness).
    ℹ️Moving shims from right to left increases backlash; moving shims from left to right decreases backlash. Record all measurements.
13. 13

    Check gear contact pattern
    Apply gear marking compound to several ring gear teeth. Rotate the pinion in both directions under light resistance to transfer the pattern. Inspect the contact pattern on the ring gear teeth. The pattern should be centered on the tooth face. If pattern is too far toward toe or heel, adjust pinion depth by changing shim thickness. If pattern is too high or low on the tooth, adjust backlash. Repeat pattern check after each adjustment until proper pattern is achieved.
    ℹ️Proper gear contact pattern is critical for differential longevity. Take time to achieve correct pattern before final assembly.
14. 14

    Final carrier bearing preload
    Once backlash and gear pattern are correct, add 0.13mm (0.005 inches) shim thickness to each side to establish carrier bearing preload. Remove carrier bearing caps, add shims, and reinstall caps. It may be necessary to use a differential spreader to reinstall the carrier with the additional preload shims. Torque carrier bearing cap bolts to specification. Verify backlash has not changed more than 0.025mm (0.001 inch). Check pinion rotating torque; total rotating torque should be 5-10 inch-pounds higher than pinion preload alone.
15. 15

    Install differential cover and refill
    Clean both differential cover and housing mating surfaces with brake cleaner. Apply continuous 3-4mm bead of RTV sealant (Motorcraft TA-357) to the differential cover flange. Install cover within 10 minutes of applying RTV. Install cover bolts and tighten in a crisscross pattern to specification. Allow RTV to cure for 1 hour before filling. Remove fill plug and add Motorcraft 75W-140 Synthetic Gear Oil through fill hole until fluid level reaches the bottom of the fill plug hole (approximately 2.0-2.5 quarts). Reinstall fill plug with torque specification.
    ℹ️Do not use excessive RTV sealant as excess can break off and contaminate the gear oil, potentially clogging passages.
    Torque spec

    Cover Bolts39 Nm (29 lb-ft)

    Fill Plug47 Nm (35 lb-ft)

Reassembly

1. Reinstall driveshaft to pinion flange, aligning the reference marks made during disassembly
2. Torque driveshaft bolts to specification in a star pattern
3. Reinstall rear wheels and torque lug nuts to specification in a star pattern
4. Lower vehicle from jack stands
5. Remove wheel chocks

Verification

• Start engine and allow to idle in Park for 30 seconds
• Shift transmission through all gears while stationary to circulate fluid
• Check for any fluid leaks around differential cover and pinion seal
• Test drive vehicle at various speeds (15, 30, 45+ mph) listening for abnormal noise, vibration, or whine
• Check for smooth acceleration and deceleration with no binding or unusual sounds
• Perform figure-eight turns in both directions to load differential under turning conditions
• After 50-100 miles of normal driving, recheck differential fluid level and inspect for leaks
• Monitor differential temperature and noise during break-in period (first 500 miles)

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