Finned cast aluminum 14-bolt rear diff cover for 2017-2025 Ford F-250 and F-350 SRW with the Dana M275 axle, with fill plug, drain plug and sight window.
A stamped steel rear cover on a 2017-and-later F-250 or F-350 Super Duty is thin, holds a modest amount of gear oil and starts to weep at the flange once the paint and sealant age. If you tow a camper or a gooseneck and your rear axle is the Dana M275 14-bolt, this finned cast aluminum cover is a direct replacement built to run cooler and make gear oil service a ten-minute job. It is part number SPELAB ASPOS08860BK in a black finish, and the box includes the cover, a gasket, 14 M10 x 1.5 hex socket bolts with a 30 mm thread length and 14 spring washers.
On the M275 the cover seals the gear oil in and doubles as the reservoir that the ring gear slings oil against before it runs back down to the pinion and carrier bearings. On a long grade with a trailer, that oil gets hot, and hot thin oil is what wears pinion bearings and cooks the additive package. This cover is deeper than the stock part, so it holds more oil, and the inside has flow channels that steer oil back toward the ring gear and bearings. The fins on the outside add surface area to shed heat into the air moving under the truck. A fill plug and drain plug let you change oil without breaking the gasket, and a sight window gives a quick level check. Overall size is 12.74 in. wide, 13.41 in. tall and 4.10 in. deep.
This is the part most buyers get wrong. Ford's Super Duty has used more than one rear axle in the 2017-and-later trucks, and Spicer's parts listing for these years covers the Ford 10.5, the Dana M275 and the larger M300 separately. Count the cover bolts first: the M275 is a 14-bolt cover, while the Ford 10.5 uses a 12-bolt cover. The M275 and M300 covers look alike and both use 14 bolts, so read the axle tag or the axle code on the door sticker to be sure. This cover does not fit F-350 dual rear wheel trucks or the 2023-2024 High Output models. If your count comes up 12 bolts, you have the Ford 10.5, and parts such as the 2011-and-up Ford 10.5 master overhaul kit and the Ford 10.5 Trac-Lok clutch set are the ones that apply to your truck.
2017-2025 Ford F-250 Super Duty and F-350 Super Duty single rear wheel trucks with the Dana M275 14-bolt rear axle. Not for F-350 DRW or 2023-2024 High Output trucks. When in doubt, send us your year and VIN or a photo of the cover and axle tag before you order. Older Super Duty trucks and the Ford 10.5 rear have their own parts, including the Super Duty 10.5 chromoly axle shaft. Gear oil and additives are in our fluids section.
Check the sight window and the bolts again after the first tow. A deeper cover takes more oil than stock, so do not stop filling at the factory capacity.
| Fits | 2017-2025 Ford F-250 and F-350 Super Duty SRW with Dana M275 14-bolt rear axle |
| Does Not Fit | F-350 DRW, 2023-2024 High Output models |
| Part Number | SPELAB ASPOS08860BK |
| Material | Cast aluminum, black finish |
| Features | Fill plug, drain plug, oil sight window, cooling fins |
| Includes | Cover, gasket, 14 M10 x 1.5 x 30 mm hex socket bolts, 14 spring washers |
| Dimensions | 12.74 x 13.41 x 4.10 in. |
| Weight | 11.53 lb (shipping) |
It fits 2017-2025 F-250 and F-350 single rear wheel trucks that have the Dana M275 14-bolt rear axle. Count the bolts on your cover and check the axle tag. A 12-bolt cover means you have the Ford 10.5, and this cover will not fit.
No. It does not fit F-350 dual rear wheel trucks or the 2023-2024 High Output models.
The cast aluminum cover, a gasket, 14 M10 x 1.5 hex socket bolts with a 30 mm thread length, and 14 M10 spring washers. Gear oil is not included.
More than the stock cover because the housing is deeper. Fill through the fill plug until oil just starts to run out of the hole rather than going by the factory capacity figure.
Only if your axle has a clutch-type limited slip. An open differential or an electronic locker does not need it. The cover itself does not change what your axle requires.
