The TDP Stage 3 Allison is engineered for Duramax owners who need a transmission that can tow hard and race harder. This unit is built to handle elevated power levels while maintaining controlled shift quality, consistent line pressure, and long-term durability when properly tuned.
Designed as the next step above a basic performance build, the Stage 3 Allison focuses on clutch capacity, hydraulic stability, and billet hard-part reinforcement to address known Allison weak points. Whether your truck is a heavy tow rig, a street-driven performance build, or a weekend race truck, the Stage 3 delivers reliable performance under abuse.
Rated up to 900 horsepower.
Raybestos or ALTO G3 C-3 & C-4 torque kits
Raybestos or ALTO G3 C-1 & C-2 torque kits
LML-style apply pistons and return springs
RatioTek pressure upgrades for improved hydraulic control
TransGo trim valves
New Torrington bearings
Billet input shaft
Billet C-2 hub
Goerend billet torque converter
Heavy-duty cast aluminum deep pan for increased fluid capacity and cooling
Modified Duramax trucks
Heavy towing with added horsepower
Street-driven performance builds
Customers wanting durability without harsh drivability
2-Year Unlimited Mileage Warranty
Warranty coverage is contingent upon:
Approved TCM calibration
Proper tire size and axle gear ratio match
Proper installation and maintenance
All warranty claims are subject to inspection and teardown verification by Thompson Diesel Performance.
Transmission tuning required
Core charge applies unless otherwise noted
Shipping not included unless specified
Built for off-road / competition-capable applications
Every TDP transmission is assembled, measured, and inspected in-house to meet our performance standards. We build for real-world reliability—not inflated ratings—so you can drive, tow, and perform with confidence.
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