There are two seals commonly referred to as rear end seals in the Ford rear differential, the pinion seal and the differential cover seal. Each of these seals will most likely fail at some point in the life of a Ford vehicle, but replacing either or both is not hard. Ford differentials should be serviced at either 45,000 or 100,000 miles, depending on the type of gear lubricant. When servicing the differential, the cover seal will be replaced, but there are times when it may leak before or after a service.
Place the drop pan under the rear differential and use the socket set to remove the bolts holding the differential cover in place. You may need to carefully pry the cover away from the differential with the screwdriver, making sure not to score the sealing surfaces or distort the cover.
Remove the bolts holding the drive shaft to the front of the differential. Pull the drive shaft away, then bend the coat hanger around the drive shaft and hang it from the frame off to the side so it does not rest on the ground.
Use your screwdriver to lever the pinion seal out of the differential, again being careful not to score or otherwise damage the sealing surface.
Install the new pinion seal. Take a large socket, roughly a 1 inch or larger that matches up to the circumference of the new pinion seal and rest it over the outer edge of the seal with the seal’s inner edge resting inside the differential. Carefully tap the socket with the rubber mallet until the seal is fully seated in the differential.
Reinstall the drive shaft.
Spray the differential cover down with brake cleaner, making sure to remove the entire old gasket and the sealing surface on the differential. If you encounter a tough spot of old gasket that will not come off, simply scrape it away with a razor blade, being careful not to cut yourself.
Wipe the cover and sealing surface on the differential down with the rags to get all the lube and gasket material off.
Place a thin bead of black RTV around the sealing surface of the differential cover. The bead should be no thicker than a ¼-inch.
Place the differential cover back on the differential and reinstall the bolts, tightening them in a crossing pattern as you would the lug nuts on a car.
Use your socket wrench, with no socket on it, to remove the fill plug from the side of the differential.
Fill the differential with the specified gear lubricant and differential additive until you can just touch it when inserting your finger into the fill hole. This should be roughly two to two and one half quarts. Make sure to use the entire bottle of additive. When done, reinsert the fill plug. Refer to your vehicle’s specific owner’s manual for fluid type and capacity. You may need to visit your local Ford parts dealer to purchase certain synthetic gear lubricants and the additive.
