Transmissions for 2001 - 2004 Chevy GMC Duramax 6.6L LB7. The Allison transmissions used in the Duramax powered GM trucks have proven themselves over the past decade. However, as with ALL transmissions they have their breaking point, no matter how you use it. And for those that looking higher horsepower or have some high miles on them. We carry a variety of stock to fully build transmission from some of the best builders in the industry, as well as torque converters and other key internal components for your transmission. Give a call so we can help you determine the right build for your truck and the best bang for your buck.