Keep your 2001-2004 Duramax 6.6L engine running at optimal temperatures to maintain peak performance. Your 6.6L puts out plenty of power, thus, it's crucial to invest in effective cooling upgrades to ensure long-term reliability. We offer a range of options, including A/C lines, upgraded coolant tanks, radiator necks, coolant bypass kits, and coolant pipes. Our selection of cooling components will help your diesel engine handle even the toughest challenges. If you're pushing your engine to the limit, make sure it gets the cooling support it needs with our top-tier upgrade kits! Further upgrade your 6.6L Duramax with our selection of Air Intake Upgrades!GM Duramax Fitments: 2001, 2002, 2003, 2004 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.