Whether you're upgrading or maintaining your GM 2500HD/3500HD's transmission, we provide a comprehensive selection of rebuild kits and internal components to simplify the process. From enhancing durability with a high-strength billet input shaft to upgrading to a high-performance overdrive clutch drum for handling extreme power, or refreshing your transmission with new gaskets, bearings, and clutches, we have everything you need! Equip your transmission with the heavy-duty internal parts and upgrades it requires to perform flawlessly in your GM 2500HD/3500HD! Pair your new rebuild kits and internal parts with our selection of Engine Upgrades!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.