This procedure covers replacement of the rear differential pinion seal on a 2015-2020 Ford F-150 with 5.0L V8 and RWD configuration to stop rear axle oil leaks.

Warnings

Tools required

Parts

• Rear differential pinion seal × 1 — Use OEM specification
• Pinion nut (recommended replacement) × 1 — Use OEM specification
• Differential cover gasket (if resealing) × 1 — Use OEM specification

Fluids

• Motorcraft 75W-140 Synthetic Gear Oil — 2 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, not axle housing
4. Remove rear wheels if additional clearance is needed
5. Place drain pan under differential
6. Clean area around pinion flange and driveshaft connection to prevent contamination

Procedure

1. 1

   Mark driveshaft alignment
   Use paint marker to mark the relationship between the driveshaft yoke and pinion flange. This ensures proper balance and phasing during reinstallation. Mark multiple reference points for clarity.
2. 2

   Remove driveshaft
   Remove the four U-joint strap bolts connecting the driveshaft to the pinion flange. Support the driveshaft and carefully slide it rearward off the pinion flange. Use a small pry bar if needed. Secure driveshaft to frame or exhaust with wire to prevent it from hanging on the center bearing.
   Torque spec

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

   Measure pinion bearing preload
   Using an inch-pound torque wrench on the pinion nut, measure and record the rotating torque required to turn the pinion. This should be 15-25 in-lbs for used bearings. This value is critical for proper reassembly. If you cannot measure this, plan to set preload by turning resistance feel during reassembly.
4. 4

   Mark pinion nut position
   Before removing the pinion nut, mark the exact position of the pinion flange relative to the pinion shaft threads using paint marker. Count and record how many threads are visible past the nut. This provides a reference point for reinstallation depth.
5. 5

   Remove pinion flange
   Use pinion flange holding tool or large pipe wrench to prevent rotation. Remove the pinion nut using appropriate socket (typically 30mm or 1-3/16 inch). Once nut is removed, carefully pull the pinion flange straight off the pinion shaft. It may require light tapping with soft mallet. Do not allow pinion shaft to drop inward or you may disturb bearing preload.
6. 6

   Remove old pinion seal
   Inspect the seal location and note the installed depth. Use seal puller or carefully pry out the old seal with large flat-blade screwdriver. Work around the perimeter to avoid damaging the housing bore. Clean the seal bore thoroughly with brake parts cleaner and inspect for damage, burrs, or grooves.
7. 7

   Inspect pinion flange
   Examine the pinion flange seal surface (the area where seal lip rides) for grooves, pitting, or damage. Any grooves deeper than 0.020 inch require flange replacement. Minor surface imperfections can be smoothed with 400-grit sandpaper. Clean flange thoroughly before reinstallation.
8. 8

   Install new pinion seal
   Lightly coat the outer diameter of the new seal with gear oil. Apply gear oil to the seal lip. Using seal driver or appropriately sized socket that contacts only the outer edge of seal, drive the seal squarely into the housing until it seats at the same depth as the original. Do not cock the seal or strike the center portion.
9. 9

   Reinstall pinion flange
   Coat pinion flange seal surface with thin layer of gear oil. Align pinion flange splines with pinion shaft and carefully slide flange onto shaft. Ensure it slides on smoothly without binding. Install new pinion nut (or cleaned original if necessary) hand-tight.
10. 10

    Tighten pinion nut to proper preload
    Using holding tool, tighten pinion nut gradually in stages. Stop frequently to check rotating torque with inch-pound wrench. Target is to achieve the original recorded preload value plus 5 in-lbs (for new seal drag). Typical final specification is 15-30 in-lbs rotating torque. Do not exceed 250 ft-lbs on pinion nut. Align flange to original marked position as reference. If preload is exceeded, you must disassemble and replace collapsible spacer.
    ⚠️Never loosen pinion nut to reduce preload. This will destroy bearing preload and require complete differential overhaul.
11. 11

    Reinstall driveshaft
    Align driveshaft yoke with pinion flange using reference marks made during disassembly. Install U-joint strap bolts and tighten evenly in crossing pattern to prevent binding. Ensure U-joint caps are properly seated in flange before final tightening.
    Torque spec

    Driveshaft U-Joint Straps20 Nm (15 lb-ft)
12. 12

    Check and refill differential fluid
    Remove differential cover fill plug (upper plug on cover or housing). Add Motorcraft 75W-140 synthetic gear oil until it reaches the bottom of the fill hole. Reinstall fill plug. Total capacity is approximately 2.0 quarts but verify fluid level at fill hole, not by quantity.

Reassembly

1. Reinstall rear wheels if removed and torque lug nuts to specification in star pattern
2. Lower vehicle from jack stands
3. Test drive vehicle at low speed in safe area, checking for vibration or noise
4. Recheck pinion nut tightness after test drive

Verification

• Inspect pinion seal area for any signs of leakage after test drive and first 50 miles
• Verify no driveline vibration or unusual noises from differential during acceleration and deceleration
• Confirm differential fluid level is correct at fill hole
• Check that driveshaft U-joint rotates smoothly without binding

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