Differential Fluids

For lubrication fluid, a very heavy oil, must be used in rear axle housings. Special hypoid oils are used in the differential case. Even another type of fluid, or oil must be used in a positraction type differential. The oil is circulated by the ring gear, and flung all over all the parts. Special troughs, or gullies are used to bring the oil back to certain spots, like the ring and pinion area and the piston bearings. The fluid is kept in with gaskets and oil seals. The bottom of the housing has a drain plug, and another filler plug is located part way up the housing. The housing must never be filled above this plug. The housing fluid lubricates some of the outer bearings, but others have lubrication fittings for the injection of wheel bearing grease. A hand gun, not a pressure grease gun must be used to grease these bearings (sparingly). A pressure grease gun could inject grease into the brakes-- greasy brakes are inefficient at best! Finally, some bearings are filled with grease at the factory and are sealed. These never require attention unless they are defective.