Ford’s Explorer SUV has a solid rear axle up to the 1999 model, and independent rear suspension from 2000 on. Changing the gear oil in the rear axle in a vehicle probably is the most neglected maintenance item, but it is part of the scheduled maintenance recommended by the manufacturer. For the Explorer, the recommended service interval is 60,000 miles. Changing the gear oil at the recommended interval enhances the longevity of the rear axle and helps prevent costly repairs later on.
Park the Explorer on a level paved surface. Place wheel chocks in front of the front wheels. Raise the rear of the Explorer with a jack and support it with a jack stand placed under each axle tube.
Place a drain pan under the center of the axle housing where the differential cover attaches to the housing.
Use a ratchet and socket to loosen all of the bolts on the cover. Remove all of the bolts except for the top three. Loosen the top three bolts until they are almost all the way out. This prevents a big splash when you break loose the cover. Use a flat-head screwdriver to carefully pry the cover loose -- just enough to break the seal. Catch the gear oil in the drain pan. Remove the rest of the bolts and remove the cover.
Remove the old cover gasket from the cover and axle housing. Use a putty knife to carefully scrape away any remaining gasket material from the cover and housing.
Spray the cover with parts cleaner and wipe it clean with a shop rag. Wipe out the inside bottom of the axle housing to remove any remaining gear oil and sludge. Spray a shop rag with parts cleaner and clean the gasket mating surface on the axle housing.
Run a bead of black RTV silicone sealant – about 1/4 inch wide – around the center of the cover. Run a bead around each bolt hole. Let the sealant set for a few minutes or as indicated on its instructions. Mount the cover on the axle housing. Install and tighten the bolts.
Use a wrench to remove the fill plug on the cover. Fill the axle with 75W-140 gear oil until the gear oil reaches the bottom of the filler hole. If you have a limited slip differential, add 4 ounces of limited slip additive before filling with gear oil. Install and tighten the filler plug.
Park the Explorer on a level paved surface. Place wheel chocks in front of the front wheels. Raise the rear of the Explorer with a jack and support it with jack stands on the frame.
Place a drain pan under the center of the rear axle. Use a ratchet to remove the drain plug from the rear cover. The ratchet head fits into the square hole in the center of the plug. Allow the gear oil to drain into the pan. Install and tighten the plug.
Use a ratchet to remove the filler plug. It is above and to the right of the drain plug. Fill the axle with 75W-140 synthetic gear oil. Use limited slip additive if needed. Install and tighten the filler plug.
