Maintenance: Replacing Rear Differential Fluid

Thanks to many of you asking, I’ve finally written about this maintenance job. Big thanks for waiting! This past year, with moving and a job change, has been crazy. I did the fluid change when my Explorer hit 67,000 miles last year, but writing about it took a bit longer.

At first, I wasn’t sure I could do it because I didn’t have the right tool. But after some looking around, I found a good, affordable pump that made the job easy.

What surprised me? Ford doesn’t have a set time for changing the rear differential fluid. But if you tow a lot or drive in tough conditions, they suggest changing the fluid every 30,000 miles.

What I used:

Step 1: Elevate Your Vehicle

For an accurate fluid measurement, it’s crucial to keep the car level. To achieve this, I elevated both the front and rear. A quick check with a water level ensured the car was perfectly horizontal.

Step 2: Locate the Rear Differential

Located above the exhaust pipes, the rear differential is straightforward to identify. For added clarity, consult the attached photo where I’ve arrowed its precise location. This visual aid should simplify the process for you.

For added clarity, I’ve also provided a close-up view of the fill bolt.

Step 3: Unfasten the Fill Bolt Using a 3/8 Ratchet Wrench

Position the 3/8 head of your ratchet wrench onto the fill bolt. Turn counterclockwise to unscrew.

Fill bolt removed.

Step 4: Drain the Old Fluid

For this, I used the “in” suction side of the transfer pump, inserting it directly into the rear differential. After draining, I transferred the fluid into a measuring cup to gauge the amount I’d removed.

Step 5: Refill with Fresh Fluid

After completely draining the old fluid, it’s time to refill. Switch the hose so that the suction end is in the new fluid bottle and the “out” end is in the rear differential’s fill port. Pump the fluid in. When you notice fluid starting to spill out, it’s an indication that the differential is full and you can proceed to seal it.

Step 6: Secure the Plug

For a leak-proof seal, I applied high-temperature thread sealant on the plug before reinstalling. This ensures a tight and safe closure.



The fluid change proved to be more straightforward than I initially anticipated, especially with the aid of the multi-use pump. However, I was taken aback when I could only drain approximately 18 oz, given the differential’s maximum capacity of 33.76 oz. Nonetheless, I’m pleased to have successfully carried out this maintenance and ensured the rear differential is now filled to the appropriate level.

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