The 2001-2004.5 model year Duramax 6600 is an
LB7, and the vehicle will have a number
1 (one) as the eighth digit of the VIN. Injectors and injector fuel return lines are beneath the valve covers.
The 2004.5- 2006.5 model year Duramax 6600 is an
LLY, and the vehicle will have a number
2 (number two) as the eighth digit of the VIN. Injectors and injector fuel return lines are outside the valve covers.
The 2006.5-2007 model year Duramax 6600 is an
LBZ, and the vehicle will have a letter
D as the eighth digit of the VIN. The LBZ virtually identical to the earlier LLY, and in-fact, the latest LLY engines are said to be the same as the LBZ, except for power/torque rating, ECM & programming and emissions certification.
The 2007.5 model year Duramax 6600 is an
LMM, and the vehicle will have a number
6 (six) as the eighth digit of the VIN. This engine runs with the newest emissions system, which includes a new Diesel Oxidation Catalyst and Diesel Particulate Filter, and requires ULSD (Ultra Low Sulfur Diesel) fuel.
More info and additional details on all of these engines can be found in one of The Diesel Page's content areas (i.e. see the
Duramax 6600 Diesel Page to learn more).
Jim