See Figures 1, 2, 3 and 4
The fluid level in the rear axle should be checked at six-month or 6,000 mile intervals. It is unnecessary to periodically drain the fluid. The factory fill should remain in the housing for the life of a vehicle, except when repairs are made. When adding to or replacing rear axle fluid, use SAE 80 hypoid gear lubricant for winter applications (-25°F), and SAE 90 hypoid gear lubricant for regular use. Limited-slip differential models require special fluid and locking differential additive. On all 1964-69 models, the fluid level should be maintained at the bottom of the filler plug hole. Starting in 1970, all models with integral carrier axles having 7 1 / 4 , 8, and 6 3 / 4 inch ring gear diameters are full when the fluid level is 1 / 4 inch below the filler hole. All other 1970 and 1971 vehicles should be filled to the filler hole. Any 1972-73 models not having 6 3 / 4 inch ring gear integral axle carriers are filled to 3 / 8 inch below the bottom edge of the filler plug hole. To check the fluid level in the axle, bend a clean, straight piece of wire to a 90° angle and insert the bent end of the wire in the axle while resting it on the lower edge of the filler hole. When checking fluid level, the axle must be at normal curb attitude.