2007.5-2010 Chevy Duramax LMM Axle & Driveline Parts

Axle and driveline on the 2007.5-2010 Silverado HD

The LMM showed up in the middle of 2007, when the HD pickups moved into the new GMT900 body. It makes 365 hp and 660 lb-ft, and in a pickup it only came behind the Allison 1000 six-speed. All of that torque lands on an AAM 11.5-inch rear axle: 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. Chevrolet's own Silverado HD brochure points at that 11.5-inch rear as the heavy-load piece of the truck. Four-wheel-drive trucks add the AAM 9.25-inch front differential, a two-piece clamshell housing hung in the torsion-bar front end and holding 1.82 quarts of 80W-90. GM listed 3.73 as the standard rear ratio on 2500HD and 3500HD; the brochure ties the 4.10 to the Vortec 6.0L gas engine, and the Eaton heavy-duty automatic locking rear differential was an option.

What fails and why

The rear axle is the strong end of this truck, and most of what we sell for it is about keeping fluid cool rather than fixing a known break. The front is the end that complains. The 9.25 clamshell is adequate at stock tire size and stock power, but its weak spots tend to surface once a Silverado is lifted and running big tires: owners commonly report front differential noise, CV and seal leaks, and bearing wear showing up after a tire upgrade rather than at a particular mileage. Gearing is the other thing that bites. Factory 3.73s stop matching the truck somewhere around 37-inch tires, and you feel it as lugging, the transmission hunting between gears, and mileage and towing performance both sliding backward.

Stock replacement vs. upgrade

For a stock-height truck that tows a fifth-wheel or a loaded gooseneck, the upgrade that earns its money is a finned cast-aluminum differential cover. Those add fluid capacity and cooling surface to the AAM 11.5, which is aimed straight at towing heat. A stock-style cover with a fresh gasket is the right call if you are only chasing a seep and the truck stays stock. If the Silverado has grown to 37-inch tires, no cover fixes the real problem: that is a gear change, roughly 4.30 to 4.56, and it is worth a phone call before you spend money anywhere else.

What we carry

Most of this page is rear differential covers and gear oil. Cast aluminum covers for the AAM 11.5 come from Pacific Performance Engineering, Mag-Hytec, BD Diesel, Wehrli Custom Fabrication and AFE in Street Series and Pro Series versions, plus the Banks Power Ram-Air cover kit. The hardware that finishes the job is here too: a PPE rear cover gasket, a WCFab cover bolt kit and an ATS Diesel Performance drain plug for their pans and covers. Merchant Automotive speed sensor connectors cover a damaged speed sensor pigtail. For fluid there is Hot Shot's Secret Blue Diamond and ADRENALINE gear oil, Lucas Oil synthetic and heavy-duty gear oil, and Royal Purple Max-Gear, in grades from 75W-90 to 85W-140. The rest of the platform sits under the Duramax hub.

Fitment notes

Put your head under the back of the truck and count the bolts on the cover before you order anything: 14 bolts means the AAM 11.5, and that is what covers and gear sets are cut for. On a 4x4, the front and rear ratios have to match, and 3.73 front and rear is the standard Duramax combination, so if someone has already re-geared one end you are matching that number instead of the brochure. The 4.10 is the one to double-check. GM's brochure lists it with the 6.0L gas engine while the aftermarket talks about 4.10 Duramax trucks, so verify by RPO tag or VIN rather than guessing. The 2011 trucks are a hard stop: the front differential was redesigned for 2011 and 2001-2010 9.25 parts do not cross, and the whole 2011 HD chassis, from frame to control arms to torsion bars and rear springs, was new, so suspension and axle parts off a later Silverado do not carry back. 3500HD trucks came single- or dual-rear-wheel, which matters for anything touching the wheel end. When in doubt, use the fitment checker on the product page or call us.

Frequently asked questions

What gear oil does the rear axle on my 2008 Silverado 2500HD take?

The AAM 11.5 rear calls for SAE 75W-90 full-synthetic gear oil, and capacity is 3.8 to 4.2 quarts. The front 9.25 differential on a 4x4 is different: 80W-90, 1.82 quarts. If a deep aluminum cover is installed, the rear holds more than the factory figure, so plan on buying an extra quart.

Is the 11.5-inch rear axle strong enough if I turn the power up?

It is the piece Chevrolet advertised as the heavy-load end of the Silverado HD: 11.50-inch ring gear, 30-spline shafts, full-float hubs. We do not have a failure pattern to report on that housing. Heat is the thing you can actually manage, and that is what the finned covers and a full-synthetic fill are for when you tow.

Do I need to re-gear if I put bigger tires on?

Once you are on 37-inch tires the factory ratio is mismatched, and it shows up as lugging, more shifting, and worse mileage and towing. The usual answer at that tire size is a gear change in the 4.30 to 4.56 range, done front and rear so the ratios stay matched. Call before you buy tires if you can, because it changes the order of operations.

Will a front differential from a 2012 Silverado work on my 2009?

No. GM redesigned the front differential for 2011, and the 2001-2010 AAM 9.25 clamshell is its own parts family. The same split applies more broadly across the 2010 to 2011 change, since the 2011 HD trucks got a new frame and new front suspension. Shop the 2007.5-2010 pages, or send us your VIN and we will confirm it.

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.