Midway through the 2004 model year, GM released the second-generation Duramax, RPO code LLY. Although much of the LLY’s internals match what you’ll find in the LB7, this version of the 6.6L V8 brought an improved injector design, variable geometry turbocharging and cleaner emissions to the table. On early versions of the LLY (’04.5-’05.5 model year GM trucks), horsepower climbed by 10 to 310hp while peak torque remained at 520 lb-ft—but became available 200 rpm sooner in the power band (1,600 rpm vs. 1,800 rpm on the LB7). Later model LLY mills (‘06), which arguably had more in common with the LBZ that followed the LLY, packed 605 lb-ft of torque.
The 2nd generation Duramax is known as the LLY. Similar to the LB7, the LLY Duramax is reliable, powerful, and lacks most of the emissions found on modern day diesel trucks like the L5P. LLY Duramax trucks don’t suffer from the same injector failure problems that LB7 trucks frequently had. Instead, many LLY Duramax problems stem from overheating. A new variable vane turbocharger and an EGR system were also added.