Axle Seal - Rear

Replace the rear axle seal on a 2021-2024 Ford F-150 3.5L EcoBoost RWD to stop differential fluid leaks at the axle shaft.

Warnings

Tools required

Parts

• Rear axle shaft seal × 1 — Use OEM Ford specification
• Differential cover gasket × 1 — Use OEM Ford specification
• RTV silicone sealant (if reusing cover) × 1 — Motorcraft TA-357 or equivalent

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 both rear wheels to improve access and reduce axle weight
5. Place drain pan under differential
6. Allow differential to cool if vehicle was recently operated

Procedure

1. 1

   Mark and remove driveshaft
   Mark the driveshaft-to-differential flange orientation with paint or marker to ensure proper reassembly alignment. Remove the four driveshaft bolts at the rear differential flange. Support the driveshaft and carefully lower it away from the differential, then secure it to the frame or suspension with wire to prevent it from hanging on the center bearing.
   Torque spec

   Driveshaft Bolts85 Nm (63 lb-ft)
2. 2

   Drain differential fluid
   Remove all differential cover bolts in a crisscross pattern, leaving the top two bolts partially threaded. Carefully break the seal with a pry bar at the bottom edge and allow fluid to drain into the pan. Once drained, remove the remaining bolts and cover. Remove and discard the old gasket material from both the cover and differential housing using a scraper and wire brush.
   ⚠Gear oil will drain quickly once cover seal is broken. Position drain pan accordingly.
   Torque spec

   Differential Cover Bolts35 Nm (26 lb-ft)
3. 3

   Remove rear brake components (if necessary)
   Remove the brake caliper and rotor from the side requiring seal replacement to gain access to the axle shaft. Support the caliper with wire or a bungee cord to avoid stressing the brake hose. This provides clearance for axle removal.
4. 4

   Remove axle shaft
   From inside the differential housing, remove the differential pinion shaft lock bolt. Remove the differential pinion shaft by pulling it outward. Push the axle shaft inward and remove the C-clip retainer from the inner end of the axle shaft. Carefully pull the axle shaft out of the housing, supporting it to prevent damage to the seal bore.
   ⚠Keep track of the C-clip retainer as it is small and easy to lose.
5. 5

   Remove old axle seal
   Using a seal puller or slide hammer with seal adapter, carefully extract the old axle seal from the axle tube. Work evenly around the seal to prevent cocking it in the bore. Inspect the seal bore for damage, burrs, or corrosion. Clean the bore thoroughly with brake cleaner and a shop towel.
   ⚠Do not damage the seal bore surface during removal as this will cause the new seal to leak.
6. 6

   Inspect axle shaft and bearing
   Carefully inspect the axle shaft seal surface for grooves, scoring, or damage. Check the axle bearing for roughness, play, or noise by rotating it by hand. If the bearing is worn or damaged, it must be replaced before installing the new seal. Minor imperfections in the seal surface can be smoothed with fine emery cloth.
7. 7

   Install new axle seal
   Lightly coat the outer diameter of the new seal with gear oil. Position the seal squarely in the bore with the seal lip facing inward toward the differential. Using a seal driver or appropriately sized socket that contacts only the outer edge of the seal, drive the seal into the bore until it is fully seated and flush with the axle tube end face. Ensure the seal is not cocked or tilted.
   ⚠Do not strike the seal face directly as this will damage the sealing element. Drive only on the outer metal edge.
8. 8

   Reinstall axle shaft
   Lightly coat the axle shaft seal surface with clean gear oil. Carefully insert the axle shaft into the housing, guiding it through the new seal without damaging the seal lip. Push the shaft fully inward until it engages with the differential side gear. Install the C-clip retainer into the groove on the inner end of the axle shaft, then pull the shaft outward to seat the C-clip against the side gear.
9. 9

   Reinstall differential pinion shaft
   Rotate the differential case to align the pinion shaft hole. Insert the differential pinion shaft and ensure it is fully seated. Install and tighten the pinion shaft lock bolt. Verify the axle shaft cannot be pulled outward, confirming the C-clip is properly engaged.
10. 10

    Install differential cover
    Clean both the differential housing and cover mating surfaces thoroughly, ensuring no old gasket material or debris remains. Install a new gasket or apply a continuous bead of RTV silicone sealant to the cover. Position the cover onto the housing and install all bolts finger-tight. Tighten the bolts in a crisscross pattern in multiple passes to the specified torque.
    ℹ️If using RTV sealant, allow 15-20 minutes cure time before filling with fluid.
    Torque spec

    Differential Cover Bolts35 Nm (26 lb-ft)
11. 11

    Refill differential
    Locate the differential fill plug on the front of the differential housing. Remove the fill plug. Using a fluid pump or squeeze bottle, add Motorcraft 75W-140 Synthetic Gear Oil until fluid begins to drip from the fill hole. The differential capacity is approximately 2 quarts, but fill to the bottom of the fill hole. Reinstall and tighten the fill plug.
12. 12

    Reinstall brake components
    Reinstall the brake rotor and caliper in the reverse order of removal. Ensure all brake hardware is properly seated and torqued to specification.
13. 13

    Reinstall driveshaft
    Align the driveshaft to the differential flange using the alignment marks made during disassembly. Install the four driveshaft bolts and tighten them to specification in a crisscross pattern to ensure even seating.
    Torque spec

    Driveshaft Bolts85 Nm (63 lb-ft)
14. 14

    Reinstall wheels and lower vehicle
    Reinstall both rear wheels and install the lug nuts hand-tight. Lower the vehicle until the tires just contact the ground. Torque the wheel lug nuts to specification in a star pattern. Fully lower the vehicle and remove jack stands.
    Torque spec

    Wheel Lug Nuts140 Nm (103 lb-ft)

Reassembly

1. Double-check that all fasteners have been reinstalled and torqued to specification
2. Verify differential fill level is correct at the fill plug hole
3. Ensure driveshaft is properly aligned and secured
4. Confirm brake components are properly reinstalled and functional

Verification

• Start the vehicle and verify no unusual noises from the differential
• Test drive the vehicle at various speeds and check for smooth operation
• After test drive, inspect the axle seal area for any signs of leakage
• Recheck differential fluid level after 50-100 miles of driving
• Monitor the area for any seepage over the next few days of normal driving

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