The 2004.5-2005 GM 6.6L Duramax LLY's are subject to running a bit hot when pushed to their limit, causing you unnecessary hassles and potential time-intensive repairs down the line. Take a look at our entire inventory of engine cooling upgrades to ensure your 6.6L Duramax LLY is operating at peak performance even during the most extreme driving applications. Outperform and outlast the competition by outfitting your GM Sierra/Silverado 2500/3500 with some of the best cooling components on the aftermarket! GM Duramax Fitments: 2004, 2005 GM 6.6L Duramax.Submodel Fitments: WT, Custom, LT, LTZ, High Country, 1LT, 2LT, Pro, SLE, SLT, AT4, Denali.Some exceptions apply, please see individual product pages for specific fitments.