SUNCOAST GM Duramax 6.6L L5P Allison Transmission 2017-2019

DIESELR SunCoast Allison Transmission (2017–2019 Duramax L5P)

The Allison 6-speed is one of the most proven heavy-duty transmissions, but in tuned L5P trucks or demanding work use, factory weaknesses show up fast. SunCoast engineered its Ranger, Guardian, and Category Series builds to correct those shortcomings with billet torque converters, GPZ clutch technology, billet steels, and hand-calibrated valve bodies.

From reliable stock replacements to extreme 950+ HP builds, each SunCoast Allison transmission is assembled by hand, vacuum-tested, and loaded with proprietary upgrades. Whether you’re towing heavy, daily driving, sled pulling, or racing, SunCoast gives you options built to match your truck’s real-world demands.

Variants

• Ranger (Stock Replacement)
  Built for stock trucks needing a direct replacement with improved durability. Includes SunCoast Guardian converter, upgraded clutch packs, steels, overhaul kit, valve body recalibration, filters, and factory deep pan. Available in 2WD and 4WD.
• Guardian Towing (Heavy-Duty Towing & Hauling)
  Designed for commercial, towing, and heavy-haul applications. Uses custom billet torque converter (or no-converter option), clutch packs, steels, overhaul kit, and recalibrated valve body. Built for reliability under long-term work conditions.
• Category 1 (500 HP)
  Performance build with custom clutch packs, steels, billet plates, and SunCoast triple-disc billet converter (converter option). Ideal for tuned street trucks, towing, and light racing up to 500 HP.
• Category 2 (600 HP)
  Adds billet input shaft and billet SFI-certified flexplate for strength. Handles sled pulling, racing, and heavy towing with aftermarket turbos. Available with or without triple-disc converter.
• Category 3 (700 HP)
  Includes billet input shaft, billet flexplate, billet P2 planet, billet C2 clutch hub, and triple-disc converter (converter option). Recommended for high-horsepower builds, sled pulling, and drag racing.
• Category 4 (950 HP+)
  Extreme build with billet input, intermediate, and output shafts, billet flexplate, billet P2 planet, billet C2 hub, and SunCoast triple-disc converter (converter option). Built for maximum reliability in 900+ HP builds and extreme competition use.