2004.5-2005 Silverado & Sierra 2500 & 3500 Duramax LLY Complete Transmissions

The Duramax LLY V8 under the hood of your HD Silverado or Sierra can make a whole ton more power and torque than stock with the right tuning, however, the stock 5-speed Allison transmission may not be thrilled with it. Tier One's built transmissions for 2004.5-2005 Silverado & Sierra 2500 & 3500 Duramax LLY trucks are designed to handle massive amounts of power and extremely tough applications without letting your big Duramax down. We replace the weak points in the 5-speed Allison with high-performance clutches, billet shafts, and hydraulic upgrades. We have a variety of Duramax LLY transmissions available that range from our HD tow transmissions that can handle heavy towing to our Duramax LLY competition transmissions that can hold over 1000 horsepower. Even the best transmission build needs a reliable connection to the engine, so if you are piecing together your own build or need a specific stall speed, look at our 2004.5-2005 Duramax LLY Torque Converters. Protect your investment from heat while towing by adding one of our 2004.5-2005 Duramax LLY Transmission Coolers. If you aren't ready for a complete transmission swap but want to fix shifting issues, a valve body replacement is a great place to start, so check out our 2004.5-2005 Duramax LLY Valve Bodies. To get the most out of your new transmission, consider upgrading your fluid capacity or installing a thermal bypass valve from our section of 2004.5-2005 Duramax LLY Transmission Parts.