Drain and refill the rear differential with fresh synthetic gear oil, inspect for leaks and metal debris, and replace the drain plug washer.

Warnings

Tools required

Parts

• Drain plug crush washer × 1 — M14 copper washer

Fluids

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

Preparation

1. Park vehicle on level, solid ground and engage parking brake
2. Place wheel chocks in front of both front wheels
3. If vehicle was recently driven, allow differential to cool for at least 30 minutes
4. Raise rear of vehicle using jack at appropriate frame lift point
5. Secure vehicle on jack stands rated for vehicle weight
6. Verify vehicle is stable before working underneath

Procedure

1. 1

   Locate differential drain and fill plugs
   Position yourself under the rear axle. Locate the drain plug on the bottom of the rear differential housing and the fill plug on the upper portion of the differential cover. Clean area around both plugs with a wire brush and shop rag to prevent contamination.
2. 2

   Remove fill plug first
   Using a 3/8" drive ratchet, loosen and remove the fill plug from the differential housing. Removing the fill plug first ensures you can refill the differential after draining. If the fill plug is seized and cannot be removed, do not proceed with draining.
   Torque spec

   Fill Plug47 Nm (35 lb-ft)
3. 3

   Drain differential fluid
   Position drain pan directly under the drain plug. Using appropriate socket, slowly loosen the drain plug. Once threads are free, quickly remove the plug by hand and allow old gear oil to drain completely into the pan. Expect approximately 2 quarts to drain. Inspect drained fluid for excessive metal particles or contamination.
   Torque spec

   Drain Plug47 Nm (35 lb-ft)
4. 4

   Inspect and clean drain plug
   Remove and discard the old copper crush washer from the drain plug. Inspect drain plug threads for damage. Clean the drain plug and surrounding area on the differential housing with a shop rag. Wipe the sealing surface clean of old washer material and debris.
5. 5

   Reinstall drain plug with new washer
   Install a new copper crush washer onto the drain plug. Thread the drain plug into the differential housing by hand to avoid cross-threading. Tighten the drain plug to specification using a torque wrench.
   ⚠Always use a new crush washer. Reusing the old washer may result in leaks.
   Torque spec

   Drain Plug47 Nm (35 lb-ft)
6. 6

   Refill differential with gear oil
   Using a fluid transfer pump or funnel with extension tube, add Motorcraft 75W-140 synthetic gear oil through the fill plug hole. Fill slowly until gear oil begins to drip from the fill hole, indicating proper level (approximately 2.0 quarts). Allow a few moments for oil to settle, then top off if necessary until oil is at the bottom of the fill hole threads.
7. 7

   Reinstall fill plug
   Wipe any spilled gear oil from the differential housing. Thread the fill plug into the housing by hand, then tighten to specification using a torque wrench. Wipe the area clean.
   Torque spec

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

   Lower vehicle and check for leaks
   Remove jack stands and carefully lower the vehicle to the ground. Start the engine and allow it to reach operating temperature. Shift through all gears including reverse. Turn off the engine and inspect the drain plug and fill plug areas for any signs of leakage.

Reassembly

1. Ensure both drain and fill plugs are torqued to specification and no tools are left under vehicle
2. Properly dispose of used differential fluid at an appropriate recycling facility

Verification

• Check for leaks around drain and fill plugs after test drive
• Verify no unusual noises from rear differential during operation
• Monitor for drips under vehicle over the next 24 hours
• Confirm proper fluid level by briefly removing fill plug - oil should be at bottom of threads

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