This procedure covers draining and refilling the rear differential with fresh gear oil on a 2015-2020 Ford F-150 with 3.5L EcoBoost engine and rear-wheel drive.

Warnings

Tools required

Parts

• Differential cover gasket × 1 — Use OEM Ford gasket or RTV silicone

Fluids

• Motorcraft 75W-140 Synthetic Gear Oil — 2 qt

Preparation

1. Park vehicle on level surface and engage parking brake
2. Place wheel chocks in front of front tires
3. Raise rear of vehicle and support securely on jack stands at frame rails
4. Allow differential to cool if vehicle was recently driven
5. Locate differential cover on rear axle housing

Procedure

1. 1

   Clean differential cover area
   Use brake cleaner and rags to clean the differential cover and surrounding area. This prevents dirt from entering the differential during service.
2. 2

   Loosen differential cover bolts
   Using a ratchet and appropriate socket, loosen all differential cover bolts in a crisscross pattern. Leave the top two bolts partially threaded to prevent the cover from falling when fluid drains.
   Torque spec

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

   Drain differential fluid
   Position drain pan beneath differential cover. Carefully remove the lower bolts first, allowing fluid to drain. Once most fluid has drained, remove remaining bolts and carefully pry cover away from housing. Allow all fluid to drain completely into pan.
   ⚠Fluid will flow out rapidly when cover is loosened. Keep hands clear of drain stream.
4. 4

   Remove old gasket material
   Use gasket scraper to carefully remove all old gasket material from both the differential housing mating surface and the cover. Ensure surfaces are completely clean and free of debris. Wipe clean with brake cleaner and lint-free rag.
5. 5

   Inspect differential components
   With cover removed, visually inspect ring and pinion gears for abnormal wear, pitting, or metal shavings. Check magnetic drain plug (if equipped) for excessive metallic debris. Normal operation will show fine gray paste; chunky metal indicates wear issues requiring further service.
6. 6

   Install new gasket and cover
   Install new differential cover gasket onto cover or apply continuous bead of RTV silicone to cover mating surface per gasket manufacturer instructions. Position cover onto differential housing, ensuring gasket remains properly aligned. Install all cover bolts finger-tight.
7. 7

   Torque differential cover bolts
   Using torque wrench, tighten differential cover bolts to specification in a crisscross pattern, working from center outward. Make at least two passes, first to half torque, then to final specification to ensure even gasket compression.
   Torque spec

   Differential Cover Bolts35 Nm (26 lb-ft)
8. 8

   Refill differential with gear oil
   Locate fill plug on differential housing (typically on front or side of housing). Remove fill plug. Using fluid pump or squeeze bottle, add Motorcraft 75W-140 Synthetic Gear Oil through fill hole until fluid begins to run out. Install and tighten fill plug. Total capacity is approximately 2.0 quarts.
9. 9

   Clean up and lower vehicle
   Wipe away any spilled gear oil from differential housing and surrounding components. Verify all bolts are properly tightened and fill plug is secure. Lower vehicle from jack stands to ground.

Reassembly

1. If RTV silicone was used instead of preformed gasket, allow proper cure time before driving (typically 1 hour minimum, 24 hours for full cure)
2. Dispose of used gear oil at appropriate recycling facility

Verification

• Start vehicle and let idle briefly, then check differential cover for any signs of leakage
• Take vehicle for short test drive (5-10 minutes) to circulate new fluid
• Re-inspect differential cover for leaks after test drive
• Check fluid level at fill plug after test drive to ensure proper fill level maintained

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