6.6L LB7 Duramax
The LB7 Duramax was first introduced for the 2001 model year as General Motors retired its 6.5L Detroit diesel. In every possible way, the Duramax was superior to the outdated Detroit and marked a revolutionary turning point for GMC and Chevrolet pickups in the diesel marketplace. 2001 also introduced the Allison 1000, arguably the first automatic transmission in its class worthy of being mated to a powerful diesel. The LB7 is unique to other Duramax models as it predates emissions regulations. As such, it’s praised for reliability and has been regarded as a particularly economical variation of the engine.
6.6L LLY Duramax
The LLY is indicative of the Duramax’s towards meeting strict emissions requirements in the U.S. while keeping the engine competitive in the market. The 2004 LLY was the first Duramax to utilize exhaust gas recirculation (EGR) and a variable vane turbocharger (VVT). The Garrett VVT provided noticeably favorable performance characteristics in comparison to the LB7’s IHI fixed geometry turbo. For the 2006 model year, the LLY underwent minor changes, yielding an 85 lb-ft improvement over the 2004/2005 model. These changes are perceived to have been made in preparation to meet future emissions requirements as well as increase torque output to maintain a competitive edge. 2006 would make the last year for the LLY, but the next generation would build upon the changes made to the Duramax platform.
6.6L LBZ Duramax
The LBZ was relatively short lived, having been available for only two model years for no concise reason other than its replacement, the LMM, was capable of meeting stricter emissions regulations rolling into effect near the time of its retirement. Mechanically, the LBZ is nearly identical to the 2006 model year LLY. However, the LBZ features more aggressive engine tuning, yielding a substantial increase in horsepower and torque over its predecessor. The LBZ produced 360 horsepower and 650 lb-ft of torque to the LLY’s 310 horsepower and 605 lb-ft. By mid-model year for 2007, the LBZ was effectively replaced by the emissions compliant, diesel particulate filter equipped LMM.