2004.5-2005 GM 2500HD/3500HD 6.6L LLY Duramax Complete Transmissions

Whether you're looking to upgrade to a high-performance transmission or replace the aging one in your 2004.5-2005 GM 6.6L Duramax, Alligator Performance has the complete transmission options you need. Our builds provide smoother gear shifts and upgraded flex plates, optimizing the performance of your Sierra/Silverado 2500HD/3500HD. Equipped with brand-new, high-efficiency components, durable torque converters, and reinforced flex plates, your diesel truck will outperform even its original factory specifications! Pair your new high performing transmission with our Crate Engines!  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.