ATS Diesel Ford Sterling 12-Bolt 10.25in Ring Gear Diff Cover

If your F-250, F-350, E-250 or E-350 has the Ford Sterling 12-bolt rear axle and you tow heavy, this ATS Diesel Protector cover, part number 402-900-3068, is built to replace the thin stamped factory cover. It is cast aluminum with a black powdercoat finish, holds about 2.5 quarts more gear oil than stock, and lets you drain and refill the axle without pulling the cover. It is a common fix for a weeping cover gasket, a dented cover and hot gear oil on long pulls with a trailer.

What a diff cover does on a Sterling axle

On the Sterling 10.25 and 10.5 the rear cover is the back wall of the gear oil sump. The ring gear dips into the oil and slings it up to the pinion bearings and carrier bearings. A stock stamped cover holds the minimum oil, gives the heat nowhere to go, and dents if it takes a hit. The ATS cover adds volume so the oil runs cooler and lasts longer, and its finned casting works as a heat sink. Cooler, cleaner oil helps the bearings and gears last longer under load.

Signs you need a new cover

• Gear oil seeping around the cover edge or a damp, dirty ring at the bottom of the housing
• A cover that is dented, cracked or rusted through from road debris or a hitch strike
• Dark, burnt-smelling gear oil after towing, a sign the oil is running hot
• No easy way to service the axle without breaking the cover seal every time
• Whine from the rear after the axle has run low on oil, which means the gears and bearings need inspection too

How to confirm it fits your axle

Count the cover bolts first. A Sterling uses 12 bolts, while the Dana 60, 70 and 80 used in other heavy-duty trucks use 10. Lugnut 4x4 notes that the 10.25 was used in 1985-1997 F-250 and F-350 pickups and that Super Duty trucks moved to the 10.5, which picked up an electronic locker option in 2011. The two share the same 12-bolt cover pattern, which is why ATS lists this cover for both. Before you order, also find the leak: oil at the pinion yoke is a pinion seal, oil at the brake backing plate is an axle seal, and only oil around the cover edge is the cover gasket. If the gears are noisy, check them now, while the cover is coming off anyway. Kits such as the Yukon master overhaul kit for the Ford 10.25 cover bearings, races and seals.

Fitment

ATS lists this cover for 1986-present Ford F-250, F-350, E-250 and E-350 with single rear wheels, in 2WD and 4WD, with the Ford 10.25 or 10.5 rear axle. Its product title shows 1986-2010, so on a newer truck check the axle tag or send us your year and VIN before ordering. Dual rear wheel trucks are not in the listed fitment. More axle hardware is on our hard parts page.

Install notes

• Park level, drain the old oil and inspect it and the old cover magnet for metal before you clean anything.
• Scrape every bit of old gasket or sealant off the housing face and degrease it. A dirty face is the usual cause of a new cover leaking.
• Install the cover with the supplied hardware, snugging the 12 bolts evenly in a cross pattern so it seats flat.
• Refill through the fill port. Plan on roughly 2.5 quarts more than your factory capacity, and use the gear oil grade and any friction modifier your owner's manual calls for, especially with a limited slip. A quart-bottle transfer pump makes filling from under the truck easy.
• Drive a few miles, then check the cover edge for seepage and recheck the bolts.
• If the old oil showed metal, fix the cause now. A Ford 10.25 master bearing kit replaces the pinion and carrier bearings.

The cover ships as a complete kit from the USA, usually the same business day, and carries our 1-year warranty.

Does it fit both the 10.25 and the 10.5 Sterling?

Yes. ATS lists it for Ford 10.25 and 10.5 rear axles. Both use the 12-bolt cover pattern.

Will it fit a dually F-350?

ATS lists single rear wheel trucks only. If you have dual rear wheels, send us your year and VIN before ordering.

How much more gear oil does it hold?

About 2.5 quarts more than the stock cover, according to ATS. Fill through the fill port until the oil reaches the correct level.

Is hardware included?

Yes. It is sold as a kit, and ATS says everything needed for installation is included.

Do I need special gear oil with this cover?

No. Use the grade Ford specifies for your axle, plus friction modifier if your owner's manual calls for it on a limited slip.

Can I change the oil without removing the cover?

Yes. ATS designed it so the axle can be drained and refilled with the cover left in place.