This procedure drains and refills the rear differential with fresh synthetic gear oil to maintain proper lubrication and extend the lifespan of the differential components.

Warnings

Tools required

Parts

• Drain plug washer × 1 — Copper crush washer for differential drain plug

Fluids

• Motorcraft 75W-140 Synthetic Rear Differential Fluid — 2 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Place wheel chocks in front of both front wheels
3. If recently driven, allow differential to cool for at least 30 minutes
4. Raise rear of vehicle using floor jack at approved lift points on frame
5. Support vehicle securely on jack stands placed under rear axle or frame
6. Verify vehicle is stable before working underneath
7. Locate differential housing at center of rear axle - drain plug is at bottom, fill plug is on driver side or rear face

Procedure

1. 1

   Clean drain and fill plug areas
   Use wire brush or scraper to remove dirt and debris from around the drain plug (bottom of differential) and fill plug (side or rear face). This prevents contamination when plugs are removed.
2. 2

   Loosen fill plug first
   Before draining, loosen the fill plug using appropriate socket. This ensures you can refill the differential after draining. If fill plug is seized and cannot be removed, do not proceed with draining. Leave fill plug loosened but in place.
   ℹ️Always verify fill plug can be removed before draining to avoid being unable to refill the differential.
3. 3

   Remove drain plug and drain fluid
   Position drain pan underneath drain plug. Using appropriate socket, remove the drain plug completely and allow differential fluid to drain fully into pan. This may take 5-10 minutes. Inspect drained fluid for excessive metal particles or debris which may indicate differential wear.
4. 4

   Clean and reinstall drain plug
   Wipe drain plug threads clean with shop rag. Discard old copper washer and install new copper crush washer onto drain plug. Thread drain plug into differential housing by hand to avoid cross-threading, then torque to specification.
   Torque spec

   Drain Plug47 Nm (35 lb-ft)
5. 5

   Remove fill plug completely
   Remove the fill plug completely from the differential housing. Ensure opening is clear of debris.
6. 6

   Refill differential with fresh fluid
   Using fluid transfer pump or squeeze bottle with hose extension, add Motorcraft 75W-140 Synthetic Gear Oil through fill hole until fluid begins to run out of fill hole. The differential is full when fluid level reaches the bottom of the fill plug opening (approximately 2 quarts total). Allow excess to drain out momentarily.
   ℹ️Fill slowly to avoid air pockets. Fluid is at correct level when it just begins to seep from fill hole.
7. 7

   Install fill plug
   Wipe fill plug threads clean. Thread fill plug into housing by hand, then torque to specification using torque wrench.
   Torque spec

   Fill Plug47 Nm (35 lb-ft)
8. 8

   Clean differential housing
   Wipe down differential housing exterior to remove any spilled gear oil. Inspect drain and fill plugs for any signs of leakage.
9. 9

   Lower vehicle
   Raise vehicle slightly with floor jack to unload jack stands. Remove jack stands and carefully lower vehicle completely to ground.

Reassembly

1. Dispose of used differential fluid at appropriate recycling facility - do not pour down drain
2. No further reassembly required for this procedure

Verification

• Start engine and drive vehicle forward and reverse for several feet to circulate new fluid through differential
• After short test drive, re-inspect drain and fill plugs for any signs of leakage
• Check differential fluid level is correct by confirming fluid is at bottom of fill plug hole when plug is removed
• Record mileage and date of service for maintenance tracking - Ford recommends differential service every 50,000 miles under normal conditions or more frequently for severe duty

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