2007.5-2010 Chevy Duramax LMM Built Transmissions

Built Allison 1000 units for the 2007.5-2010 Silverado HD

The Allison 1000 six-speed is the only transmission GM put behind the LMM in these pickups, so a complete unit is a replacement in kind, built stronger rather than swapped for something else. The sequence of upgrades normally ends here: TCM calibration first, then a billet-cover multi-disc converter, then the valve body, and a built unit last. Buying the assembly skips straight to the end, which makes sense when the stock transmission has already failed. A stock LBZ/LMM-era Allison runs out of room around 430 to 450 rwhp and 850 to 900 lb-ft, and the stock converter is usually what quits first; its thin stator cracks and the soft front cover balloons, and the debris that comes off contaminates the fluid and damages the rest of the unit.

When a complete unit beats piecing it together

Three situations point this way. The transmission is already down with metal in the fluid. The truck is tuned or towing at the top of what the stock unit will take, where slipping in the C3 gears and limp mode locked in third become routine. Or the shifts have gone soft with age because valve body valves are sticking in worn bores, pump gears have lost efficiency and the bushings are worn, and you would rather fix all of it once. A built unit comes with the internals that have proven out on these: a billet C2 hub, a billet P2 planetary, a PTO cover that routes oil to the C3 clutches, hardened pump gears, bronze bushings and genuine Allison solenoids.

What we carry

BD Diesel builds the Allison transmission and converter assembly listed here for 2007.5-2010 trucks, and Calibrated Power / DuramaxTuner supplies a built Allison with a matched torque converter for the LMM. Both arrive as a complete assembly with the converter included rather than as a bare case. The engine side of the truck lives on our Duramax pages.

Fitment and ordering notes

Built units are assembled for either 2WD or 4WD and the two are not interchangeable, so confirm your drivetrain before the order goes in. Expect a core charge, which is how these are sold; your old transmission goes back. Plan on TCM calibration as part of the install, because an Allison that is not commanded correctly will find limp mode no matter how strong the internals are. Also note the 2010/2011 split: 2011 HD trucks moved to the LML with a new frame, suspension and driveline, so a 2011-and-up listing is not a substitute. If you want it installed, we do this work in our own bays in Wildwood, FL.

Frequently asked questions

Why does a built Allison come with a core charge?

Because these are sold as an exchange. The builder needs cases and hard parts coming back to build the next unit, so the core charge is refunded when your old transmission is returned. Factor the core return into your timeline, since the truck has to be apart before the old unit can ship.

Do I need TCM tuning with a built transmission?

Yes. TCM calibration is part of a built-transmission install, not an accessory. Limp mode locks the Allison in third when it sees excessive slip, high temperature or heavy load, and an ECM calibration without matching TCM work will trigger it quickly even on fresh hardware.

Is a built unit necessary at my power level?

If you are under roughly 430 to 450 rwhp and 850 to 900 lb-ft and the transmission is healthy, usually not. At that level the better money is TCM calibration, a converter and a valve body, in that order. Past it, or once converter debris has gone through the fluid, a complete built unit with a matched converter is the repair that lasts.

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.