Differential Rebuild - Rear

Complete disassembly, inspection, and rebuild of the rear differential assembly including ring and pinion setup, bearing replacement, and seal installation for the 1972 Ford F-100.

Warnings

Tools required

Parts

• Pinion bearing kit (inner and outer bearings with races) × 1 — Use OEM specification
• Carrier bearing set (side bearings with races) × 1 — Use OEM specification
• Pinion seal × 1 — Use OEM specification
• Differential cover gasket × 1 — Use OEM specification or RTV sealant
• Pinion nut × 1 — Use OEM specification - one-time use
• Ring gear bolt set × 1 — Use OEM specification
• Carrier shim kit × 1 — Use OEM specification
• Pinion shim/spacer kit × 1 — Use OEM specification
• Crush sleeve (if applicable to your axle) × 1 — Use OEM specification
• Axle seals (both sides) × 2 — Use OEM specification
• Ring and pinion gear set (if replacing gears) × 1 — Match gear ratio - typically 3.00, 3.50, or 4.10

Fluids

• 80W-90 GL-5 rear differential oil — 3.5 qt

Preparation

1. Park vehicle on level ground and apply parking brake firmly
2. Chock the front wheels securely on both sides
3. Raise rear of vehicle with floor jack and support on jack stands under frame rails
4. Remove both rear wheels
5. Place drain pan under differential housing
6. Clean exterior of differential housing thoroughly to prevent contamination during rebuild
7. If reusing ring and pinion, mark the contact pattern side of ring gear teeth with paint or marker for reference

Procedure

1. 1

   Drain differential fluid and remove cover
   Remove the differential cover bolts (verify exact count for your axle housing). Note: if your axle is a Ford 9-inch removable-carrier (banjo) type, there is no serviceable rear cover — the third member is unbolted and removed from the front of the housing after draining. Carefully break the seal and allow gear oil to drain completely into the drain pan. Remove the cover and gasket material. Inspect drained fluid for metal particles, which indicate gear or bearing wear. Clean the cover and mating surface on the housing with a gasket scraper and brake cleaner.
2. 2

   Remove axle shafts
   Remove the 4 bolts securing each axle shaft retainer plate to the brake backing plate (accessible from behind the brake assembly on each side). Carefully pull both axle shafts straight out from the axle tubes. A slide hammer with axle puller attachment may be required to extract the shafts and pressed-on bearings. Keep axle shaft seals and bearings with their respective shafts if reusing. Verified detail (On the 1972 F-100 with a Ford 9-inch or integral-carrier axle, axle shafts are typically retained by a retainer plate bolted at the backing plate (brake end), NOT accessed through the differential case. The C-clip retention on many integral axles requires removing the differential pinion shaft first. The described 'through the case opening' access does not match a bolt-on retainer plate axle.): Remove the axle shaft retainer plate fasteners at the brake backing plate on each side (verify count and access point for your specific axle). If your axle uses C-clip retention, first remove the differential pinion shaft lock bolt and pinion shaft, then push each axle shaft inward and remove the C-clip before withdrawing the shaft. Carefully pull both axle shafts straight out from the axle tubes. Keep axle shaft seals and bearings with their respective shafts if reusing.
3. 3

   Mark and remove carrier bearing caps
   Using a punch or marker, clearly mark the carrier bearing caps and their corresponding positions on the housing (left/right and orientation). Remove the 4 carrier bearing cap bolts (2 per cap). Carefully remove both bearing caps. Note the thickness and position of any shims behind the carrier bearings - these determine backlash and must be tracked precisely.
4. 4

   Remove differential carrier assembly
   Carefully lift the complete carrier assembly (differential case with ring gear attached) out of the housing. The carrier bearings will remain on the carrier. Keep all carrier shims organized and labeled by side (left/right). Measure and record the original shim thickness on each side for reference during reassembly.
5. 5

   Remove pinion nut and flange
   Mark the relationship between the pinion flange and pinion shaft for reference. Using the pinion holding tool to prevent rotation, remove the pinion nut. Use a suitable puller or carefully tap the pinion flange to remove it from the pinion shaft. Note the number of exposed threads on the pinion shaft or measure the depth of the flange position for reassembly reference.
6. 6

   Remove pinion assembly
   Tap the pinion shaft from the rear (differential side) to drive it forward out the flange opening of the housing. The pinion will come out with the inner bearing, crush sleeve (if equipped), and pinion depth shim. Catch these components carefully. Remove the pinion seal from the housing using a seal puller or slide hammer. Remove the outer pinion bearing race from the housing front.
7. 7

   Remove and inspect all bearings and races
   Using the bearing race driver or press, remove the inner pinion bearing race from the housing. Remove the carrier bearings from the differential case using a bearing puller or press. Remove the inner pinion bearing from the pinion shaft if still attached. Inspect all bearings, races, and gear surfaces for pitting, scoring, discoloration, or unusual wear patterns. Any damage requires replacement.
8. 8

   Disassemble differential case (if replacing internal components)
   Remove the 10 ring gear bolts and separate the ring gear from the carrier using a soft-face mallet if necessary. Drive out the differential pinion shaft lock pin from the case. Remove the pinion shaft, spider gears, and side gears from the case. Inspect all components for wear, chips, or cracks.
9. 9

   Clean and prepare all components
   Thoroughly clean the differential housing, carrier case, and all reusable components with brake cleaner or solvent. Remove all old gasket material, sealant, and metal particles. Inspect the housing for cracks, especially around bearing bores and mounting surfaces. Clean all gear teeth with solvent and inspect for damage.
10. 10

    Install new bearing races
    Using the appropriate bearing race driver, install the new outer pinion bearing race into the housing front bore, driving it until fully seated. Install the new inner pinion bearing race into the housing rear bore. Install the new carrier bearing races into their respective bores on each side of the housing. Ensure all races are fully seated without cocking or damage.
11. 11

    Determine pinion depth and install pinion bearings
    Install the correct pinion depth shim on the pinion shaft (use shim that came with new gear set or calculate from markings on pinion head). Press the new inner pinion bearing onto the pinion shaft. Install the pinion with inner bearing into the housing from the front (flange side), seating the pinion into the inner bearing race. Install the crush sleeve or solid spacer over the pinion shaft. Install the outer pinion bearing onto the pinion shaft. Coat new pinion seal lips with gear oil and drive the seal into the housing using a seal driver until flush.
12. 12

    Install pinion flange and set preload
    Install the pinion flange onto the pinion shaft, aligning any reference marks if reusing components. Install the new pinion nut and tighten gradually using the pinion holding tool. Check pinion bearing preload with the inch-pound torque wrench as you tighten - rotate the pinion several times between checks. Target preload is 15-25 inch-pounds for new bearings (8-12 inch-pounds for used bearings). Once correct preload is achieved, do not back off the nut as this will collapse the crush sleeve incorrectly.
13. 13

    Reassemble differential case with ring gear
    If disassembled, install the side gears and spider gears into the differential case with the pinion shaft. Install the pinion shaft lock pin and stake or peen it securely. Clean ring gear and carrier mating surfaces thoroughly. Position the ring gear on the carrier, ensuring proper alignment. Install the ring gear bolts (verify exact count for your axle) with thread locker and tighten in a cross-pattern to factory specification (verify torque against service manual; commonly 70-85 ft-lb for this class of axle). Note: some Ford 9-inch ring gears use left-hand-thread bolts — verify thread direction before removal and installation.
14. 14

    Install carrier bearings and determine shim thickness
    Press the new carrier bearings onto the differential case (one on each side). Install the carrier assembly into the housing with the original shim pack on each side as a starting point. Install the bearing caps in their marked positions. Snug the bearing cap bolts to hold assembly in position but do not fully tighten yet.
15. 15

    Set ring gear backlash and carrier bearing preload
    Install a dial indicator with the plunger contacting the ring gear tooth face. Check backlash at 4 positions around the ring gear by rotating the pinion while rocking the ring gear. Target backlash is 0.005-0.008 inches. Adjust by moving shims from one side of the carrier to the other - removing shims from the ring gear side moves the gear closer to the pinion (reduces backlash). Once backlash is correct, add 0.004-0.006 inches of shims equally to both sides to create carrier bearing preload. Install bearing caps and torque bearing cap bolts to specification (typically 60-80 ft-lb for this housing).
16. 16

    Check gear tooth contact pattern
    Apply gear marking compound to 8-10 teeth on the ring gear. Rotate the pinion in both directions under light load (use a wrench on the pinion nut to create resistance). Examine the contact pattern on the teeth. The pattern should be centered on the tooth face, slightly toward the toe (smaller end). If the pattern is off, adjust pinion depth shims (moves pattern toward heel or toe) or carrier shims (moves pattern toward top or bottom of tooth). Repeat marking and adjustment until pattern is correct.
17. 17

    Install new axle seals
    Using a seal driver or large socket, carefully drive new axle seals into each axle tube until seated flush with the axle housing end. Coat the seal lips with gear oil before installation. Ensure seals are driven in straight without cocking or damage to the sealing lip.
18. 18

    Reinstall axle shafts
    Carefully slide each axle shaft into its respective axle tube, ensuring the splines engage with the differential side gears. Push the axle shaft in until the bearing is fully seated against the housing. Rotate the axle shaft as needed to align the retainer plate bolt holes with the backing plate. Install the 4 retainer bolts on each side and torque to specification (typically 30-40 ft-lb).
19. 19

    Install differential cover and fill with gear oil
    Install a new gasket or apply a continuous bead of RTV sealant to the differential cover mating surface. Position the cover on the housing and install all 10 cover bolts. Tighten in a cross-pattern to specification (typically 25-35 ft-lb). Allow RTV to cure per manufacturer instructions if used. Remove the fill plug from the housing and fill with 80W-90 GL-5 gear oil until oil reaches the bottom of the fill hole (approximately 4-5 pints / 2.0-2.5 quarts — fill to hole level rather than by volume; verify against service manual). Install and tighten the fill plug.

Reassembly

1. Reinstall both rear wheels and torque lug nuts to specification (typically 75-85 ft-lb for this vehicle)
2. Lower vehicle from jack stands to ground
3. Test drive the vehicle at various speeds, listening for abnormal gear noise or vibration
4. After 500 miles of break-in, drain and refill the differential oil to remove metal particles from gear break-in

Verification

• Check for any gear oil leaks around the differential cover, pinion seal, and axle seals
• Verify no abnormal whining, howling, or clunking noises from the differential during operation
• Confirm smooth engagement and no binding when turning corners
• Re-check differential oil level after initial test drive to ensure proper fill level
• Verify no excessive heat build-up in the differential housing during normal driving

More procedures for this vehicle