This procedure covers the removal, inspection, and replacement of the limited slip clutch pack in the rear differential of a 2015-2020 Ford F-150 with the 3.5L EcoBoost V6 engine.

Warnings

Tools required

Parts

• Limited slip clutch pack kit × 1 — Use OEM specification for 9.75" rear axle
• Differential cover gasket × 1 — Use OEM specification
• Friction modifier additive × 1 — Motorcraft XL-3 or equivalent
• Pinion seal (if damaged) × 1 — Use OEM specification
• Side bearing shims (assortment) × 1 — Use OEM specification

Fluids

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

Preparation

1. Park vehicle on level surface and chock front wheels securely
2. Raise rear of vehicle and support on jack stands at frame rails
3. Remove rear wheels using appropriate socket
4. Allow differential to cool if vehicle was recently operated
5. Clean exterior of differential housing to prevent contamination during disassembly
6. Verify you have the correct clutch pack kit for the 9.75" rear axle before beginning

Procedure

1. 1

   Drain differential fluid
   Place drain pan under differential cover. Remove all differential cover bolts in a crisscross pattern. Carefully pry cover loose and allow gear oil to drain completely. Inspect drained fluid for metal particles or debris that may indicate additional wear issues.
   Torque spec

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

   Remove driveshaft
   Mark driveshaft orientation to pinion flange for reinstallation. Remove the four U-joint strap bolts securing driveshaft to pinion flange. Support driveshaft and carefully slide rearward to separate from transmission. Secure driveshaft out of work area.
   Torque spec

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

   Remove axle shafts
   Remove the axle shaft retaining bolts from both sides of the differential. Carefully pull both axle shafts partially out of the differential housing (approximately 6 inches) to clear the differential carrier. Support axles to prevent damage to brake lines or ABS sensors.
4. 4

   Remove differential carrier assembly
   Remove the carrier mounting bolts securing the differential carrier to the axle housing. Carefully pry the carrier assembly loose and remove from housing. Place carrier on a clean workbench. Note the location and thickness of any shims behind the carrier bearing caps for reassembly reference.
   ⚠Carrier assembly is heavy (approximately 40 lbs). Use proper lifting technique or get assistance.
   Torque spec

   Mounting Bolts31 Nm (23 lb-ft)
5. 5

   Disassemble differential carrier
   Mark bearing caps with punch marks for orientation. Remove bearing cap bolts and carefully remove caps. Use differential spreader tool to carefully spread carrier just enough to remove differential case (maximum 0.010 inch spread). Remove ring gear and differential case assembly. Do not over-spread carrier as this will cause permanent damage.
   ⚠️Never spread differential carrier more than 0.010 inch. Excessive spreading will permanently damage the carrier casting.
6. 6

   Remove ring gear and disassemble case
   Remove ring gear bolts from differential case. Use soft hammer to tap ring gear off case if necessary. Drive out the differential pinion shaft roll pin using appropriate punch. Remove pinion shaft, then remove pinion gears and side gears. Keep all components organized and note their orientation.
7. 7

   Remove old clutch packs
   Remove the clutch pack assemblies from both sides of the differential case. Note the exact order and orientation of friction discs and steel plates. Count all components and compare to new clutch pack kit to verify completeness. Inspect case for scoring or damage in clutch pack areas.
8. 8

   Clean and inspect components
   Thoroughly clean differential case, side gears, pinion gears, and all related components with parts cleaner. Inspect case for cracks or excessive wear. Inspect side gear and pinion gear teeth for damage. Measure case bore diameter and side gear hub clearance to verify within specifications. Replace any worn or damaged components.
9. 9

   Install new clutch packs
   Soak new clutch pack friction discs in 75W-140 gear oil for 15 minutes before installation. Install new clutch packs in exact sequence specified in kit instructions, alternating friction discs and steel plates. Ensure all tabs are properly engaged in case slots. Install side gears into clutch packs, ensuring proper engagement.
   ℹ️Clutch pack installation sequence is critical. Verify against kit instructions. Typical sequence starts with a friction disc against the case.
10. 10

    Reassemble differential internals
    Install pinion gears and thrust washers into case, meshing with side gears. Rotate side gears to align pinion shaft holes. Install pinion shaft through case and gears. Verify all gears rotate smoothly. Install new roll pin to secure pinion shaft. Verify pin is fully seated below case surface.
11. 11

    Install ring gear and set up carrier
    Heat ring gear to approximately 200°F to aid installation. Align ring gear to case and install bolts in star pattern. Torque ring gear bolts to manufacturer specification (typically 100-110 ft-lbs in multiple stages). Install carrier bearings onto case if removed. Install assembly into carrier with spreader tool, ensuring shims are in original positions.
12. 12

    Check and adjust backlash
    Install bearing caps in marked positions. Tighten bearing cap bolts to specification. Mount dial indicator to measure ring gear backlash. Check backlash at four points around ring gear. Backlash should be 0.005-0.008 inch. Adjust by moving shims from one side to the other as needed. Recheck backlash after any shim changes.
    ℹ️Moving shims from left to right increases backlash. Moving shims from right to left decreases backlash. Maintain total shim thickness.
13. 13

    Verify gear pattern
    Apply gear marking compound to several ring gear teeth. Rotate pinion through several revolutions in both directions while applying resistance. Check tooth contact pattern on ring gear. Pattern should be centered on tooth face. Adjust shim pack if necessary to achieve proper pattern.
14. 14

    Install carrier into axle housing
    Clean axle housing thoroughly and install carrier assembly with original shims. Install carrier mounting bolts and torque to specification. Slide axle shafts back into position, ensuring they fully engage the side gears. Install axle shaft retaining bolts.
    Torque spec

    Mounting Bolts31 Nm (23 lb-ft)
15. 15

    Reinstall driveshaft and fill differential
    Align driveshaft to pinion flange using reference marks made during removal. Install U-joint strap bolts and tighten evenly. Clean differential cover and housing mating surfaces thoroughly. Apply thin bead of RTV sealant to cover or install new gasket. Install cover and torque bolts in star pattern. Fill differential with 2.0 quarts of Motorcraft 75W-140 synthetic gear oil plus 4 oz friction modifier additive. Install fill plug and torque to specification.
    ℹ️Limited slip differentials require friction modifier additive to prevent chatter. Do not omit this additive.
    Torque spec

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

    Differential Cover Bolts35 Nm (26 lb-ft)

Reassembly

1. Install rear wheels and torque lug nuts to 140 Nm (103 lb-ft) in star pattern
2. Lower vehicle to ground
3. Verify differential fill level is correct with vehicle on level surface
4. Dispose of used gear oil according to local environmental regulations

Verification

• Test drive vehicle at low speed in safe area, making several gradual turns in both directions to verify proper limited slip operation
• Listen for abnormal whining, grinding, or chattering noises from differential
• Check for fluid leaks around differential cover and pinion seal after test drive
• Limited slip should engage smoothly during turns without chatter or binding
• Recheck differential fluid level after 50-100 miles of driving and top off if necessary

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