How to Change the Gear Oil on a 2003 Ford F-150 Rear Endby Tim Petruccio
The Ford F-150 first began its relationship with the American public in 1975. The 2003 Ford F-150 came equipped with a 4.2-liter V-6 and two-wheel drive, in its base model. Optional engines in the 2003 F-150 included two-versions of the 4.6-liter V-8 and four-versions of the 5.4-liter V-8. Found in the center of the rear axle housing, the rear differential in the 2003 Ford F-150 requires the use of fully synthetic gear oil. Use a friction modifier in the rear end differential as well in order to increase the anti-friction properties of the differential fluid.
Raise the rear of the F-150 using a jack. Place jack stands beneath the rear axle housing, just inside both rear wheels. The farther you place the jack stands apart, the more stability you will have for this project. Lower the truck onto the jack stands.
Lie beneath the rear bumper of the truck and slide yourself into position to access the rear differential. Visually inspect and locate the rear-differential fill plug. If the plug is not on the rear of the differential, the plug will be on the upper driver's side of the differential, facing the front of the car. Remove the plug with a 1/2-inch drive ratchet placed directly onto the head of the plug.
Place a drain pan or empty 1-gallon container beneath the differential. Insert the vacuum end of a pump siphon into the differential fill hole and slide the tube to the bottom of the differential. Place the other end of the pump siphon into the drain pan, or an empty 1-gallon bottle.
Pump the siphon repeatedly until you have completely emptied the rear differential. The siphon hose will make a gurgling sound, when the differential is empty.
Add 4 oz. of friction modifier to the gear oil, if the gear oil does not have the modifier already included. Add 1 3/4 qts. of 75-140w full-synthetic gear oil to the rear differential if you have an 8.8-inch rear-end identified by 10-bolts on rear cover. Add 2 1/2 qts. of 75-140w full-synthetic gear oil if you have a 9.75-inch rear end identified by 12-bolts on the rear cover.
Replace the gear-oil fill plug, and tighten the plug snug with a 1/2-inch ratchet. Do not over tighten the fill plug, as there is no stopper on the plug. Turn the plug a quarter turn beyond the snug point to ensure the plug seals the rear differential.
Lift the rear of the truck off of the jack stands, and then remove the stands from beneath the truck. Lower the truck to the ground.
- Certain gear oil brands such as Mobil 1 and Royal Purple, have 75-140w full-synthetic gear oil that already contains a friction modifier. Using these products would eliminate the need to purchase and have to measure the right amount of friction modifier separately. These products cost slightly more than without the modifier already included.
Things You'll Need
- 1 ton or greater capacity jack
- 2 jack stands
- 1/2-inch drive ratchet
- Hand pump or electric pump siphon
- 1-gallon drain pan, or empty 1-gallon jug
- 75-140w full synthetic gear oil (1.75-quarts for 10 bolt rear, 2.5-quarts for 12 bolt rear)
- 4 ounces friction modifier (If not included in the gear oil)
- Do not over fill the rear differential with fluid. Adding more fluid than is recommended can cause excess pressure, which can permeate and destroy the rear end seals and gasket.
Tim Petruccio is a professional writer and automotive mechanic. His writing combines more than 20 years of mechanical experience in automotive service, service management, automotive education and business ownership. He assisted in the automotive beta, which launched March 2011.