The rear differential in a 2006 Ford F-150 houses the ring and pinion gears. The differential uses these gears to transmit torque from the driveshaft to the axle shafts to turn the rear wheels. As the ring, pinion and axles ride on one another, they create a tremendous amount of friction and wear. The differential contains a synthetic 75w-140 weight gear lubricant to combat the effects of friction, wear and heat. The tremendous forces placed on this fluid cause it to break down over time, necessitating replacement. Ford recommends servicing the rear differential at 60,000 miles.
Apply the 2006 Ford F-150's parking brake and set the transmission in park. Brace the right-front wheel with two wheel chocks.
Lift the rear end of the F-150 with the floor jack. Place the jack stands under the rear axle out by the leaf spring perches. Lower the F-150 onto the jack stands.
Position the drain pan directly below the rear cover on the rear differential. Loosen the fill plug from the side of the rear differential using a socket wrench. Remove the rear cover retaining bolts from the lower portion of the rear cover using a socket wrench and 13 mm socket. Allow the old fluid to pour out of the differential into the drain pan.
Remove the remaining rear cover bolts when all the old fluid has drained into the drain pan. Scrape the old gasket material from the rear cover and differential sealing surfaces using a gasket scraper. Clean the sealing surfaces with brake cleaner and a rag.
Apply a 1-cm bead of black RTV all the way around the rear differential cover's sealing surface. Place the cover on the rear differential and bolt it in place with the torque wrench and socket, tightening the bolts in a crossing pattern to 35 foot-pounds.
Remove the fill plug from the side of the rear differential. Pour two and a half quarts of 75w-140 synthetic gear lube into the differential. Slowly add more fluid until the new fluid reaches the bottom lip of the fill hole; 8.8 and 9.75 rear ends will take approximately 5.5 pints, 10.25 rear ends will take 6.9 pints.
Reinstall the fill plug with the socket wrench. Spray brake cleaner on the differential and wipe off any spilled lubricant with a rag. Remove the drain pan from underneath the F-150.
Lift the truck off the jack stands with the floor jack. Remove the jack stands and set them aside. Lower the F-150 to the floor and then remove the wheel chocks before operating the truck.
