Axle Seal - Rear

This procedure covers the replacement of the rear axle shaft seal on a 2015-2020 Ford F-150 with 3.5L EcoBoost and RWD, requiring removal of the axle shaft and seal replacement.

Warnings

Tools required

Parts

• Rear axle shaft seal × 1 — Use OEM specification
• Differential cover gasket (if damaged) × 1 — Use OEM specification
• Differential cover bolts (if corroded) × 10 — Use OEM specification

Fluids

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

Preparation

1. Park vehicle on level ground and engage parking brake
2. Chock front wheels securely
3. Allow differential to cool completely if vehicle was recently driven
4. Gather all tools and parts before beginning
5. Position drain pan under rear differential

Procedure

1. 1

   Remove rear wheel
   Loosen lug nuts while vehicle is on the ground. Raise the rear of the vehicle on the side requiring seal replacement using a floor jack. Support securely with jack stands under the frame rail. Remove the wheel and set aside.
   Torque spec

   Wheel Lug Nuts140 Nm (103 lb-ft)
2. 2

   Drain differential fluid
   Position drain pan under differential. Remove the differential cover bolts in a crisscross pattern, loosening the top bolts last. Carefully pry the cover away from the housing and allow all gear oil to drain completely. Remove the cover and gasket material.
   ⚠Gear oil will flow out quickly once the cover is loosened. Keep hands and drain pan positioned appropriately.
   Torque spec

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

   Clean differential housing and inspect
   Use shop rags to wipe excess oil from the differential housing opening. Inspect the ring and pinion gears for abnormal wear or metal debris. If excessive wear or debris is present, further diagnosis is needed before continuing.
4. 4

   Remove axle shaft retaining hardware
   Inside the differential housing, locate the C-clip or retaining bolt that secures the axle shaft. On this model, push the axle shaft inward slightly to access the C-clip. Remove the pinion shaft lock bolt, then remove the pinion shaft. Push the axle shaft inward and remove the C-clip from the button end of the axle shaft.
5. 5

   Remove axle shaft
   Carefully pull the axle shaft straight out of the axle housing tube. The shaft is heavy and may bind slightly as the bearing passes through the seal area. Support the shaft weight to prevent dropping. Set the axle shaft on a clean surface and inspect the bearing and seal surface for wear or damage.
   ⚠The axle shaft weighs approximately 15-20 lbs and can drop suddenly. Maintain control during removal.
6. 6

   Remove old axle seal
   Using a seal puller or slide hammer with hook adapter, carefully extract the old seal from the axle tube. Work carefully to avoid damaging the axle tube bore surface. If the seal is difficult to remove, use the slide hammer with steady force. Clean the seal bore thoroughly with shop rags and inspect for scoring or damage.
7. 7

   Install new axle seal
   Lightly coat the outer diameter of the new seal with gear oil. Position the seal squarely in the axle tube opening 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 place until it seats flush with the axle tube face. Ensure the seal is installed straight and completely seated.
   ⚠Do not strike the seal face directly as this will damage the seal. Drive only on the outer metal edge.
8. 8

   Inspect and prepare axle shaft
   Clean the axle shaft seal surface thoroughly with a shop rag. Inspect for grooves, scoring, or rust that could damage the new seal. Light surface rust can be cleaned with fine emery cloth, but deep grooves require axle shaft replacement. Coat the seal contact area and bearing surface with clean gear oil.
9. 9

   Install axle shaft
   Carefully slide the axle shaft into the axle tube, guiding it through the new seal and bearing. Push the shaft in until it reaches the differential side gears. Align the splines and push firmly until the shaft fully engages. Push the axle shaft inward and install the C-clip on the button end. Pull the axle shaft outward to seat the C-clip in the side gear.
10. 10

    Reinstall pinion shaft
    Insert the pinion shaft through the differential case and side gears, ensuring it passes through the center of the spider gears correctly. Align the lock bolt hole and install the pinion shaft lock bolt. Torque the lock bolt to specification per Ford service data (typically 20-34 Nm, but verify with service manual if available).
11. 11

    Install differential cover
    Clean all gasket material from the differential housing mating surface using a wire brush or gasket scraper. Install a new differential cover gasket (use RTV silicone if gasket is not available). Position the cover and install all bolts hand-tight. Torque the differential cover bolts in a crisscross pattern to specification.
    Torque spec

    Differential Cover Bolts35 Nm (26 lb-ft)
12. 12

    Refill differential with gear oil
    Locate the differential fill plug on the front of the differential housing. Remove the fill plug. Add Motorcraft 75W-140 Synthetic Gear Oil through the fill hole until fluid begins to drip from the fill hole opening. The differential is full when fluid reaches the bottom of the fill plug hole. Install and tighten the fill plug.
13. 13

    Reinstall wheel and lower vehicle
    Install the wheel onto the hub. Install lug nuts and tighten in a star pattern by hand. Lower the vehicle until the tire contacts the ground. Torque the lug nuts to specification in a star pattern. Lower the vehicle completely and remove jack stands.
    Torque spec

    Wheel Lug Nuts140 Nm (103 lb-ft)

Reassembly

1. Ensure all differential cover bolts are torqued to specification in the correct pattern
2. Verify differential is filled to the proper level at the fill plug
3. Double-check that wheel lug nuts are torqued in a star pattern
4. Wipe any spilled gear oil from the differential housing and axle components

Verification

• Test drive the vehicle for 10-15 miles, including several stops and turns to work the differential
• Re-check the differential fluid level at the fill plug after test drive
• Inspect the axle seal area and differential cover for any signs of leakage
• Monitor the seal area over the next few days of normal driving to confirm repair success
• Check wheel lug nut torque after 50-100 miles of driving

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