2020-2024 Silverado & Sierra 2500 & 3500 6.6L Duramax L5P Complete Transmissions

Your 2020-2024 Silverado or Sierra 2500/3500 Duramax L5P can make a whole heck of a lot of power with only a few performance modifications, but that doesn't mean your truck's Allison 10L1000 transmission is ready to hold it. Tier One's selection of built 10L1000 transmissions feature a ton of upgrades and reliability improvements that allow you to use aggressive tuning, big turbos, and fuel upgrades without your transmission letting you down. We have 10L1000 transmissions that range from budget-friendly towing builds with reliability fixes all the way to powerful performance transmissions that can hold upwards of 800 crankshaft horsepower. Whether you tow heavy or race, Tier One has the solution to keep your L5P moving. 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 2020-2024 Duramax L5P Torque Converters. Protect your investment from heat while towing by adding one of our 2020-2024 Duramax L5P Transmission Coolers. If you aren't ready for a complete transmission swap but want to fix shifting issues or known factory defects, a valve body replacement is a great place to start, so check out our 2020-2025 Duramax 10L1000 Valve Bodies. To get the most out of your new transmission, consider upgrading your fluid capacity or installing a deep pan from our section of 2020-2024 Duramax L5P Transmission Parts.