This procedure covers the replacement of the ring and pinion gears in the rear differential of a RWD 2021-2024 Ford F-150 with the 3.5L EcoBoost V6 engine, including differential disassembly, gear installation, and proper setup.

Warnings

Tools required

Parts

• Ring and pinion gear set with installation kit × 1 — Match axle ratio to VIN specification
• Pinion bearing kit (inner and outer bearings and races) × 1 — Often included with gear set
• Pinion seal × 1 — Use OEM specification
• Crush sleeve or solid spacer (depending on design) × 1 — Use OEM specification
• Differential bearing set (side bearings) × 1 — Use OEM specification
• Differential cover gasket or RTV sealant × 1 — Motorcraft TA-31 or equivalent
• Pinion nut × 1 — Use new, one-time use
• Ring gear bolts × 1 — Use new if not included in kit

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
5. Place drain pan under differential
6. Mark driveshaft and pinion flange orientation for reassembly alignment
7. Have all specialized tools and new parts ready before beginning disassembly

Procedure

1. 1

   Drain differential and remove cover
   Remove differential cover bolts and allow gear oil to drain completely into drain pan. Clean cover and housing mating surfaces thoroughly. Inspect old gear oil for metal particles indicating previous gear damage.
   Torque spec

   Differential Cover Bolts35 Nm (26 lb-ft)
2. 2

   Remove driveshaft
   Remove driveshaft bolts at the pinion flange. Support driveshaft and carefully slide it rearward to separate from pinion flange. Secure driveshaft out of the way or remove completely from vehicle.
   Torque spec

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

   Mark and measure original gear pattern
   Rotate ring gear and apply gear marking compound to several teeth. Rotate pinion through the ring gear to create contact pattern. Document pattern with photos. Use dial indicator to measure ring gear backlash at multiple points around the gear (should be 0.13-0.20mm typically). Record pinion rotating torque using inch-pound torque wrench.
4. 4

   Remove pinion flange and seal
   Use pinion holding tool to prevent rotation. Remove pinion nut (note: this is not the axle nut). Mark pinion flange position relative to pinion shaft. Use appropriate puller to remove pinion flange. Remove and discard old pinion seal. Carefully tap pinion rearward out of housing, catching it as it releases from front bearing.
5. 5

   Remove ring gear from carrier
   Install differential case spreader and spread case only enough to access carrier bearings (typically 0.25mm maximum spread). Remove differential carrier bearing caps, marking left and right orientation. Carefully remove carrier assembly from housing. Remove ring gear bolts from carrier and separate ring gear. Inspect carrier for wear or damage.
6. 6

   Remove old bearings and races
   Use bearing race puller to remove pinion bearing races from housing. Use press or bearing puller to remove bearings from pinion shaft and carrier. Remove crush sleeve from pinion shaft and discard. Clean all components thoroughly and inspect housing for cracks or damage.
7. 7

   Install new pinion bearings and determine shim thickness
   Press new inner and outer pinion bearing races into housing, ensuring they seat completely. Use pinion depth gauge tool to determine correct shim thickness for proper pinion depth based on markings on new pinion gear. This is critical for proper gear mesh. Shim value is typically etched on pinion head (e.g., +2 or -3).
8. 8

   Assemble and install pinion
   Install selected shim(s) on pinion shaft. Press inner pinion bearing onto shaft. Install pinion into housing from rear. Install new crush sleeve (or solid spacer with correct shim if applicable), outer bearing, pinion seal, and flange. Install new pinion nut and tighten gradually while checking pinion rotating torque with inch-pound wrench. Target preload is typically 16-29 in-lbs for new bearings. Do not over-tighten as crush sleeve cannot be reused.
9. 9

   Install ring gear on carrier
   Clean ring gear and carrier mating surfaces. Install ring gear on carrier, aligning bolt holes. Install new ring gear bolts with thread locker and tighten in star pattern to specification per installation kit instructions (typically 95-115 Nm). Allow thread locker to cure per manufacturer instructions.
10. 10

    Install carrier bearings
    Press or drive new side bearings onto carrier, ensuring they seat fully against carrier shoulders. Do not use old bearings as they have worn to the old gear pattern.
11. 11

    Install carrier assembly and set backlash
    Install carrier assembly into housing. Install bearing caps in correct orientation (as marked during removal). Use differential case spreader to slightly spread housing if needed. Install bearing adjusters and tighten until zero backlash is achieved. Back off adjusters and reset to achieve proper backlash of 0.13-0.20mm measured with dial indicator at ring gear teeth. Typically adjust both sides equally to center ring gear under pinion.
12. 12

    Check and verify gear pattern
    Apply gear marking compound to ring gear teeth. Rotate pinion through mesh in both forward and reverse directions under light load. Check contact pattern on gear teeth. Pattern should be centered on tooth face. Adjust pinion depth (shims) if pattern is too high or low on tooth. Adjust backlash if pattern is too far toward toe or heel of tooth. Repeat until proper pattern is achieved across multiple teeth.
13. 13

    Install differential cover
    Clean cover and housing mating surfaces completely. Apply new gasket or RTV sealant per manufacturer instructions (if using RTV, apply 3-4mm bead). Install cover and bolts. Tighten bolts in star pattern to specification.
    Torque spec

    Differential Cover Bolts35 Nm (26 lb-ft)
14. 14

    Reinstall driveshaft and fill differential
    Align driveshaft with pinion flange using marks made during disassembly. Install driveshaft bolts and torque to specification. Fill differential through fill hole with Motorcraft 75W-140 Synthetic Gear Oil until oil reaches bottom of fill hole (approximately 2 quarts). Install fill plug. If equipped with limited slip, add appropriate friction modifier additive.
    Torque spec

    Driveshaft Bolts85 Nm (63 lb-ft)
15. 15

    Reinstall wheels and perform break-in
    Install rear wheels and torque lug nuts in star pattern to specification. Lower vehicle from jack stands. Perform initial test drive at moderate speeds, avoiding heavy acceleration or towing for first 500 miles to allow gears to properly seat.
    Torque spec

    Wheel Lug Nuts140 Nm (103 lb-ft)

Reassembly

1. Ensure all bearing preloads are set correctly before final assembly
2. Double-check gear contact pattern before installing cover - incorrect pattern will destroy gears quickly
3. Use new crush sleeve or appropriate solid spacer - never reuse
4. Verify backlash is within specification at multiple points around ring gear
5. Apply thread locker to ring gear bolts as specified in installation kit

Verification

• Check for gear oil leaks around cover and pinion seal after installation
• Listen for abnormal whining or grinding noises during test drive
• Verify smooth operation in both acceleration and deceleration
• Recheck differential oil level after 50-100 miles of operation
• Monitor gear temperature during break-in period - excessive heat indicates improper setup
• After 500-mile break-in, drain and refill with fresh gear oil to remove metal particles from initial gear seating

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