This procedure covers draining and refilling the rear differential fluid on a 2015-2020 Ford F-150 with RWD, including inspection of the differential cover and gasket replacement.

Warnings

Tools required

Parts

• Differential cover gasket or RTV sealant × 1 — Motorcraft TA-31 RTV Sealant or equivalent OEM gasket
• Drain plug washer (if drain plug equipped) × 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. Allow differential to cool if vehicle has been recently driven (minimum 30 minutes)
3. If additional clearance is needed, safely raise and support the rear of the vehicle on jack stands
4. Locate the rear differential cover at the center of the rear axle assembly
5. Verify whether your differential has a drain plug or requires full cover removal

Procedure

1. 1

   Position drain pan and remove fill plug
   Locate the fill plug on the differential cover (typically upper position). Use appropriate socket to loosen and remove the fill plug first to ensure you can refill the differential after draining. Position drain pan underneath the differential cover.
2. 2

   Drain differential fluid
   If equipped with drain plug: Remove the drain plug and drain fluid completely into pan. If no drain plug: Loosen all cover bolts gradually in a crisscross pattern, then remove all bolts except the top two. Carefully pry the cover loose at the bottom to allow fluid to drain into the pan. Once drained, remove the remaining bolts and cover.
   Torque spec

   Cover Bolts42 Nm (31 lb-ft)

   Drain Plug51 Nm (38 lb-ft)
3. 3

   Clean differential cover and housing surface
   Remove all old gasket material or RTV sealant from both the differential cover and the axle housing mating surface using a gasket scraper. Be careful not to gouge the aluminum surfaces. Clean surfaces thoroughly with brake cleaner and wipe dry with clean rags. Inspect the cover for damage or warping.
   ⚠Do not allow debris or old gasket material to fall into the differential housing. Cover the opening with a clean rag if needed.
4. 4

   Inspect differential internals
   With cover removed, visually inspect the ring and pinion gears for excessive wear, scoring, or metal debris. Check for metal shavings or particles in the drained fluid. Small amounts of fine metallic material are normal, but large chunks or excessive debris may indicate internal damage requiring professional assessment.
5. 5

   Prepare and install differential cover
   If using RTV sealant: Apply a continuous 3-4mm bead of Motorcraft TA-31 RTV sealant around the cover mounting surface, circling inside the bolt holes. If using gasket: Position new gasket on cover. Install cover onto differential housing, ensuring proper alignment. Thread all cover bolts by hand first.
   ℹ️If using RTV sealant, allow 10-15 minutes for initial setup before tightening bolts, but complete installation within the sealant's working time (typically 30 minutes).
6. 6

   Torque cover bolts
   Tighten all cover bolts in a crisscross pattern to ensure even compression of the gasket or sealant. Torque bolts to specification in multiple passes: first to 50% of final torque, then to full specification.
   Torque spec

   Cover Bolts42 Nm (31 lb-ft)
7. 7

   Install drain plug if equipped
   If your differential has a drain plug, install a new drain plug washer onto the plug. Thread the drain plug into the cover by hand, then torque to specification.
   Torque spec

   Drain Plug51 Nm (38 lb-ft)
8. 8

   Refill differential with gear oil
   Using a fluid pump or funnel with hose inserted into the fill plug hole, add Motorcraft 75W-140 Synthetic Gear Oil. Fill until fluid begins to drip from the fill hole. The differential is full when fluid reaches the bottom of the fill plug threads (approximately 2.0 quarts total). Allow a few minutes for fluid to settle and top off if necessary.
9. 9

   Install fill plug
   Clean the fill plug threads and install the fill plug. Torque to specification.
   Torque spec

   Fill Plug51 Nm (38 lb-ft)
10. 10

    Clean up and lower vehicle
    Wipe down the differential cover and surrounding area to remove any spilled gear oil. If vehicle was raised, carefully lower it from jack stands. Properly dispose of old differential fluid according to local regulations.

Reassembly

1. If RTV sealant was used, allow it to cure for at least 1 hour before driving the vehicle
2. Check for leaks around the differential cover and fill plug after the initial test drive

Verification

• Start the vehicle and allow it to idle for 1-2 minutes to circulate the new fluid
• Inspect the differential cover, drain plug (if equipped), and fill plug for any signs of leakage
• Test drive the vehicle for 5-10 miles, then re-inspect for leaks while the differential is warm
• Listen for any abnormal noises from the rear axle during normal driving and turning

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