Replacing or upgrading the transmission of your 2001-2005 diesel Chevy or GMC truck is easy with Next Gen Diesel. We have various 2001-2005 Allison Duramax transmissions models to choose from, making it easy to find one that meets your needs. Our selection includes street, superstock, and competition models to choose from. If you want a transmission that is compatible with a powerful diesel engine, opt for the competition model. This transmission suits engines with horsepower up to 1500. If you primarily use your truck for light commuting and don’t need a ton of power, we recommend the superstock Allison transmission. This model is compatible with engines up to 550 horsepower. Check out our selection of 2001-2005 Allison Duramax transmissions today!