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6.6L Duramax Diesel FAQ


Who makes the Duramax Diesel?

The 6.6L Duramax was designed by and is manufactured by DMAX Ltd, a joint venture between General Motors and Isuzu created in December of 1998. Isuzu was responsible for the design of the engine itself, while GM engineers carried out the task of building and integrating the engine's electronic control systems for their Silverado and Sierra pickups. General Motors is currently the majority stakeholder in DMAX Ltd. All 6.6L Duramax diesels are assembled by DMAX in Moraine, Ohio.


How many version of the Duramax have been made?

6 versions of the 6.6L Duramax have produced, but there are other "Duramax" engines in existence, both domestically and Internationally. The 7.8L Duramax inline 6, for example, is based on the Isuzu 6H series. A 2.8L and 2.5L inline 4 cylinder Duramax is used outside of the United States in a number of applications.


What was used in GMC/Chevrolet pickups before the Duramax?

Chevrolet first experimented with a diesel option by offering the 5.7L Oldsmobile diesel in the 1970's. The Olds proved extremely unreliable and was more or less a disaster. From there, GM began offering the Detroit 6.2L in the early 80's. The engine was designed to deliver excellect fuel mileage and as such it wasn't much of a workhorse. It would later be replaced by the 6.5L, which despite higher power levels, had difficulty competing.


Which Duramax do I have?

• 2001 - 2003 model years only used the LB7.

• 2004 model year had either an LB7 and LLY, which was introduced midyear.

• 2005 model year trucks had the LLY.

• 2006 model year trucks had the LLY or the LBZ.

• 2007 model year trucks had the LBZ or the LMM.

• 2008 - 2010 model years had the LMM.

• 2011 - current model years had the LML, except chassis cab trucks which received the detuned LGH.


If you have a model year in which more than one version was offered, you can identify the engine using your VIN number and our decoder: Which Duramax do I have