2007.5-2010 Chevy Duramax LMM Differential Parts

The differentials under a 2007.5-2010 Silverado HD

Two housings, two jobs. The rear is an AAM 11.5: an 11.50-inch ring gear, 30-spline shafts, a 14-bolt cover, and 3.8 to 4.2 quarts of SAE 75W-90 full-synthetic gear oil. GM published 3.73 as the standard rear ratio on 2500HD and 3500HD, with the Eaton heavy-duty automatic locking rear differential available as an option. On a 4x4 the front is an AAM 9.25 clamshell carrying 1.82 quarts of 80W-90, with ratios listed from 3.42 through 4.56 across these model years. The front housing is a 2001-2010 part family and was redesigned for 2011, so those parts do not cross; the rear AAM 11.5 stayed under GM HD trucks well past 2010.

Covers, fluid, and when gearing is the real answer

Most differential work on a stock Silverado HD is a seeping cover and a fluid change, and a stock-style cover with a fresh gasket does that job. Towing changes the math. A finned cast-aluminum cover adds fluid capacity and cooling area to the AAM 11.5, which is the whole point of it when you are pulling weight in Florida heat. The other decision is gearing, and tire size drives it: factory 3.73s stop matching the truck at around 37 inches, which shows up as lugging, extra shifting and softer towing. The fix at that tire size is a ring-and-pinion change in the 4.30 to 4.56 range at both ends, not a different cover.

What we carry

Cast aluminum rear covers for the AAM 11.5 from Pacific Performance Engineering, Mag-Hytec, Wehrli Custom Fabrication, BD Diesel and AFE in Street Series and Pro Series versions, plus the Banks Power Ram-Air cover kit. Hardware to finish the job: a PPE rear cover gasket, a WCFab cover bolt kit and an ATS Diesel Performance drain plug that fits their pans and covers. Gear oil is on this page as well, from Hot Shot's Secret in Blue Diamond and ADRENALINE, Lucas Oil in synthetic and heavy-duty grades, and Royal Purple Max-Gear, in viscosities from 75W-90 to 85W-140. The rest of the platform is under the Duramax hub.

Fitment notes

Count the cover bolts: 14 means AAM 11.5. On 4x4 trucks the front and rear ratios must match, and 3.73 front and rear is the standard Duramax pairing, so verify what is actually in your truck by RPO tag or VIN. GM's brochure lists the 4.10 with the gas engine, and a truck that has already been re-geared will not match any brochure. Nothing on this page is a 2011-and-newer front differential part. Use the fitment checker on the product page if you are not sure.

Frequently asked questions

How much gear oil does the rear differential hold?

Plan on 3.8 to 4.2 quarts of SAE 75W-90 full synthetic for a stock AAM 11.5. A deep finned aluminum cover increases that, so buy an extra quart when you swap one on. The front 9.25 differential on a 4x4 is separate: 1.82 quarts of 80W-90.

Is an aluminum differential cover worth it on a truck that tows?

That is the case where it makes sense. The finned covers add fluid volume and cooling surface to the AAM 11.5, which is aimed at towing heat. On a stock Silverado that never sees a trailer, a stock-style cover and the correct fluid is enough.

Can I run a heavier gear oil than 75W-90 in the rear?

Start from the factory grade. The AAM 11.5 rear is specified as 75W-90 full synthetic and the front 9.25 as 80W-90. The heavier grades on this page, 80W-110 and 85W-140, are stocked because other axles and equipment call for them. If you want to deviate from spec, call the shop and tell us how the truck is used before you buy.

Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.