Use hypo id gear lubricant SAE 80 or 90, adding 2 oz. of Ford part No. EST-M2C118-A friction modifier for models with a front locking differential, and for those with a rear locking differential, use Ford part No. ESP-M2C154-A locking differential fluid along with 4 oz. of Ford part No. EST-M2C118-A friction modifier. The fluid level in the drive axles should be checked at each oil change, as the rear axle lacks a dipstick; instead, a filler plug is located in the side of the housing. To check the fluid level, ensure the transmission is in park or in gear, set the parking brake, and block the drive wheels. If necessary, raise the vehicle using jack stands to ensure it is level. Clean the area around the fill plug, remove it, and check that the gear oil is at the bottom of the fill hole, adding more lubricant if needed. For Traction-Lok limited-slip units, include 4 oz. of Ford Friction Modifier CBAZ-198546-A. Drain and refill the drive axle housings every 100,000 miles or after driving in high water. The best method for draining is to remove the axle housing cover, ensuring the oil is at normal operating temperature. If a drain plug is present, it can be serviced similarly to a manual transmission. To drain, drive the vehicle until the lubricant is warm, raise and support it if needed, and use a suction gun if no drain plug is available. Clean the area around the differential, position a drain pan, and loosen the housing cover bolts to allow the lubricant to drain. After draining, clean the gasket surfaces, install a new gasket and sealant on the housing cover, tighten the bolts in a crisscross pattern, and refill the drive axle housing with the appropriate lubricant before checking for leaks.