Whether you’re upgrading to a high-performance transmission or replacing the aging one in your 2006-2007 GM 6.6L Duramax, Alligator Performance has you covered with our complete transmission options. These builds offer smoother gear shifts and upgraded flex plates, maximizing the performance of your Sierra/Silverado 2500HD/3500HD. With brand-new, high-efficiency components, durable torque converters, and reinforced flex plates, your diesel truck will perform better than ever—surpassing even its original factory condition! Pair your new high performing transmission with our Crate Engines!GM Duramax Fitments: 2006, 2007 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.