DURAMAX L5P TRANSMISSION

CHEVY/GM DURAMAX L5P TRANSMISSION

Ready to upgrade your L5P Allison? Find the right performance transmission, converter, or component for your 2017+ Duramax — from complete RoadMaster and TowMaster packages to billet flexplates and Xtrude cooling.

  • 2017+ L5P DURAMAX

    Solutions for Chevy/GMC Silverado & Sierra 2500/3500 HD trucks.

  • ALLISON 1000 SPECIALISTS

    Remanufactured transmission packages, converters, and hard parts.

  • BILLET FLEXPLATES

    Handle increased torque and prevent cracking with our SFI-approved flexplates.

  • ENHANCED COOLING

    Keep transmission fluid temperatures in check with Xtrude coolers and bypass deletes.

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FIND THE RIGHT TRANSMISSION PARTS FOR YOUR L5P

This table provides a general guide to our transmission parts for the 6.6L L5P Duramax. Find your model year to see typical parts and applications. Always confirm specific vehicle fitment on the individual product page before ordering.

ApplicationEngineCommon YearsTypical ProductBest For
Chevy/GMC 2500/3500 HD6.6L L5P Duramax2017-2019TowMaster/RoadMaster Transmission & Converter PackageComplete, bolt-in replacement for towing or daily driving.
Chevy/GMC 2500/3500 HD6.6L L5P Duramax2017-2019Duramax Allison FlexplatePreventing cracks and failures with modified engines or heavy towing.
Chevy/GMC 2500/3500 HD6.6L L5P Duramax2017-2019Allison Cooler Bypass DeleteEnsuring maximum flow to aftermarket transmission coolers.
Universal / Custom Builds6.6L L5P Duramax2017+Xtrude Transmission Cooler with FanAdding auxiliary cooling for demanding applications and builds.

WHY YOUR ALLISON 1000 NEEDS SUPPORT AND HOW BD SOLVES IT

The Allison 1000 transmission paired with the 6.6L L5P Duramax is a robust combination from the factory, but it has its limits, especially when subjected to increased power levels or heavy, consistent towing. The stock torque converter can be a weak point, and fluid temperatures can rise quickly under load, accelerating wear on clutches and internal components. Upgrading key parts can dramatically improve the longevity and performance of your transmission.

  • HIGH FLUID TEMPERATURES

    The stock cooling system can be overwhelmed when towing heavy loads, especially up grades, leading to fluid breakdown and premature wear.

    The BD Difference

    An auxiliary Xtrude cooler keeps fluid temperatures in check under heavy towing and extends transmission life.

  • CRACKED FLEXPLATE

    Increased power from tuning or the stress of heavy towing can crack the stock flexplate, causing noise and eventual driveline failure.

    The BD Difference

    A billet steel, SFI-approved flexplate is a permanent fix built to handle increased torque loads.

  • CONVERTER SHUDDER & SLIPPAGE

    This often occurs under heavy load or with added horsepower, indicating the stock converter can't handle the torque.

    The BD Difference

    An upgraded, multi-disc torque converter provides superior holding power for towing and added power.

  • TRAILER MANEUVERABILITY

    Backing a heavy trailer, especially uphill or around tight corners, can be difficult without the torque of low-range, since the 4WD system binds on pavement.

    The BD Difference

    The 2-Low UnLoc Kit lets you engage 4-Low without binding the front driveline on high-traction surfaces.

What is the difference between your RoadMaster and TowMaster transmission packages?

Both are comprehensive, remanufactured packages with upgraded components and a torque converter. The main difference lies in the build specifications for clutches and internal components, tailored for different power levels and uses. Check the product descriptions for specific details.

Is a billet flexplate necessary for my L5P Duramax?

The factory flexplate is stamped steel and a known failure point, especially on trucks with performance tunes or those that tow frequently. Our billet flexplate is significantly stronger and SFI-approved to prevent cracking.

Do I really need an aftermarket transmission cooler?

If you frequently tow heavy loads, live in a hot climate, or have increased your engine's horsepower, an auxiliary cooler is highly recommended. Keeping fluid temperatures down is the single best way to prolong the life of your Allison transmission.

What does the Allison Cooler Bypass Delete do?

The factory thermal bypass valve can restrict flow to the cooler, even when the fluid is hot. Our delete kit ensures 100% of the fluid is sent through the cooler circuit at all times for maximum cooling efficiency, which is especially important when adding an aftermarket cooler.

What is the 2-Low UnLoc kit for?

This kit gives you access to the 4-Low gear range without engaging the front axle. This is perfect for backing up heavy trailers or maneuvering at low speeds on high-traction surfaces like pavement, where normal 4WD would cause driveline binding.

Are your transmission packages new or remanufactured?

Our transmissions are fully remanufactured in-house. Each unit is disassembled, cleaned, inspected, and rebuilt with upgraded clutches, seals, and a recalibrated valve body, plus a new BD torque converter.