The differential is a component of the powertrain system, which consists of the transmission, clutch (or torque converter) differential, and axle shafts. The purpose of the differential is to send torque and power to the wheels. It adjusts the power using gears to accommodate for driving types such as turning and accelerating from a stop. The oil in the differential is essential to ensure gears and axles work properly.
The correct oil for the 2000 F-350 is SAE 75w-140gl synthetic gear oil; the Ford 10.50-inch axle, the Dana 80 axle, requires SAE 75w-90QL synthetic gear lubricant; and the Dana 135 axle requires SAE 80w-90QL synthetic gear oil. Oil capacity is determined by filling the differential until a small amount of fluid begins to leak from the differential oil check plug. Once the oil begins to leak out of the hole, no more fluid should be added.
The differential oil is essential in providing wheel power to the vehicle. The oil is used in the differential to keep friction down and reduce wear on the gears. It serves as a coolant and lubricates the gears. Fluid should be checked every 15,000 miles or every 12 months, whichever comes first. The fluid can be checked by removing the check/fill plug from the differential. The fluid must be even with the bottom of the fill/check hole; if not, add fluid until it reaches bottom of hole.
It is recommended that the differential oil be changed every 60,000 miles or 48 months, whichever comes first. When changing the differential oil, the vehicle should be driven until it is warm; warm oil will drain easier. There are two options when removing differential fluid. One method is to suck fluid out of the differential with a suction pump out of the check/fill hole. The second method is to remove the differential cover drain and then replace it. If you are removing the differential drain cover, you must replace the differential cover gasket. Remove the cover bolts using a ratchet and socket. Pull the cover off, and clean the surface. Reinstall the cover gasket and bolts, and tighten the bolts down. Fill it with fluid to capacity according to specifications.
