Ford 10.25 Inch Limited-Slip Differential

NOTE: Refer to Rear Antilock Brakes for diagnostic and testing procedures regarding the excitor ring on the differential case on F-series and Bronco vehicles equipped with rear Antilock brakes. For excitor ring service procedures, refer to Integral Carrier Axle-10.25 Inch Ring Gear.

If roughness or noises such as chatter are present while turning corners, the probable cause is incorrect or contaminated lubricant.

Before a differential is removed and disassembled for chatter concerns, the lubricant level and grade should be determined.

Refill the axle with the specified quantity of Hypoid Gear Lubricant, EOAZ-19580-A (ESP-M2C154-A) or equivalent and add 0.237L (8 ounces) of Additive Friction Modifier, C8AZ-19B546-A (EST-M2C118-A) or equivalent friction modifier for rear axles. Warm the axle up and recheck for chatter by making a minimum of ten figure-eight type turns.

Noise Acceptability

A gear-driven unit (especially on a drive axle) will produce a certain amount of noise. Some noise is acceptable and may be audible at certain speeds or under various driving conditions. For example, as on a newly paved blacktop road. The slight noise is in no way detrimental to the operation of the rear axle and must be considered normal.

NOTE: For vehicles equipped with a limited-slip differential a slight stick-slip noise on tight turns after extended highway driving is considered acceptable and has no detrimental effect.

If this is unsuccessful, a complete lubricant drain, flush and refill will usually correct chatter. The following procedure is recommended to ensure that the system is flushed of old lubricant:

1. Warm the lubricant by vehicle road operation or five minutes of operation in gear with both rear wheels off the ground on a hoist.

WARNING: A VEHICLE EQUIPPED WITH A LIMITED-SLIP DIFFERENTIAL WILL ALWAYS HAVE BOTH WHEELS DRIVING. IF ONE WHEEL IS RAISED OFF THE FLOOR AND THE REAR AXLE IS DRIVEN BY THE ENGINE, THE WHEEL ON THE FLOOR COULD DRIVE THE VEHICLE OFF THE STAND OR JACK. ALWAYS BE SURE THAT BOTH WHEELS ARE OFF THE GROUND.

2. Drain lubricant while warm. Remove cover to drain completely. If cover is removed, it will be necessary to replace gasket at this time.

3. Clean the gasket mating surface of the rear axle carrier casting and cover.

Apply a new continuous bead of Silicone Rubber (D6AZ-1 9562-AA or equivalent) to the carrier casting face inside the cover bolt holes.

CAUTION: Make sure machined surfaces on both cover and carrier are clean and free of oil before installing the new silicone sealant. Inside of axle must be covered when cleaning the machined surface to prevent contamination.




4. Install cover and tighten cover bolts to 34-47 Nm (25-35 ft-lb) as shown. Tighten the cover bolts in a cross-wise pattern to insure uniform draw on cover.

NOTE: Cover assembly must be installed within 15 minutes of application of the silicone or new sealant must be applied.

5. Add lubricant through the fill hole until the lubricant level reaches the bottom of the fill hole with the axle in the running position (approximately 6.5 U.S. pints). For out-of vehicle repairs, add 7.5 U.S. pints of lubricant. Install the fill plug and tighten to 20-41 N m (15- 30 ft-lb).

6. Operate the vehicle for approximately 16 km (10 miles), making at least ten figure-eight turns to flush the old lubricant out of the clutch packs.

7. Repeat Steps 2, 3, 4 and 5, making sure to replace cover gasket.

8. It is possible that a slight chatter, requiring additional vehicle operation may remain after Step 5. If chatter still persists after 160 km (100 miles) of operation, or remains severe after Step 6 above, disassembly and repair will be necessary.

For further diagnostic and testing procedures refer to General Driving Axle Service.