2020-2025 Allison 10L1000 800HP Transmission

Tier One's Stage 3 10L1000 Transmission Features:

• Built 10L1000 Transmission designed for heavy towing, hauling, and high-horsepower street use
• Handles 800+ horsepower from aggressive Duramax tuning, turbo upgrades, and bolt-on mods
• Complete, drop-in transmission for your 2020+ Silverado or Sierra 2500HD/3500HD Duramax
• Includes a High Capacity "E" Clutch Drum with Billet Apply Piston, 4140 steel dowels, Hard Anodized F Clutch Cylinder "Trashcan", Pro Loc Valve Body & Pump assembly, deep transmission pan, & performance overhaul kit
• Fixes common 10L1000 problems like "E" drum deflection, "F" clutch failure, and spline wear while allowing you to stack on serious power
• Features a Deep Cast Aluminum Pan for increased fluid capacity and cooling
• Valve bodies are dyno-tested and modified for increased line pressure and lube flow
• Backed by a 2-year, unlimited mileage warranty
• Requires additional core charge and freight shipping
• If you have questions or want a custom 10L1000 build, contact Tier One or call 602-399-5484!
• Tier One's premier 10L1000 transmission option

Built 10L1000 Transmission that Handles Huge Horsepower and Heavy Duty Work Environments

It's not hard to get the 6.6L Duramax under the hood of your 2020+ Chevy or GMC 2500/3500 churning out a ton more horsepower and torque. While the factory Allison 10L1000 was a revolutionary step forward, the stock transmission struggles to handle the rigors of heavy towing and high-horsepower tuning over time. Tier One's Stage 3 10L1000 transmission is our solution for durability and performance, engineered to let your Duramax hit huge levels of power and handle the toughest challenges your work environment throws its way. The Tier One Stage 3 built 10L1000 transmission is built to handle over 800 horsepower, making it capable of holding power from aggressive tuning and heavy loads without skipping a beat. On top of improved power handling, we here at Tier One also include all the hardware and components necessary to fix common issues—specifically the "E" clutch drum deflection and "F" clutch wear—so that your truck gets clean shifting and reliable operation. The Stage 3 10L1000 transmission is the perfect choice for Duramax owners who are hauling heavy loads, towing frequently, or navigating rough terrain. This build comes with both high-strength internal components and hydraulic improvements that work together to ensure your truck can safely make a ton of power and use that power whenever and wherever you need.

Includes a Full Suite of Billet Components and Performance Transmission Parts to Reliably Hold Big-Time Horsepower

The Tier One Stage 3 Transmissions are built with care by technicians that have decades of combined experience in the performance transmission market. Each unit starts its life as a factory core that is fully disassembled, cleaned, and thoroughly inspected. We address the 10L1000Â’s weakest link by installing a High Capacity "E" Clutch Drum. This upgraded drum features a Billet 6061 aluminum apply piston that is significantly larger than stock to eliminate "coning" and deflection. We also replace the malleable factory aluminum splines with 4140 steel dowels, preventing the steels from digging into the drum. This design increases clutch capacity by 29% over OEM. Tier One also installs a new OEM F Clutch Cylinder "Trashcan" that we take the extra step of hard anodizing. This hard anodized coating hardens the surface where the clutches spline, preventing the clutch teeth from digging into the aluminum and ensuring vastly improved reliability. The heart of the Stage 3 10L1000 is the Pro Loc Valve Body and Pump assembly. We modify the pump to increase main line pressure by up to 60psi for massive clamping force, and we boost the lube circuit pressure from 6psi to 20psi (a 250% increase) to keep the planets and bushings cool under load. We also utilize Raybestos Powertrain GPZ frictions throughout the build, including adding an extra clutch to the "F" clutch pack (bringing it from 4 to 5 clutches) to handle the abuse of 3rd to 4th gear shifts. Each transmission comes with a Deep Cast Aluminum Pan that holds 4 quarts more fluid than stock and features cooling fins to dissipate heat.

Fully Overhauled 10L1000 Transmission for Excellent Reliability

During our build of your Stage 3 10L1000 transmission, we here at Tier One go over every millimeter of its internal components to guarantee excellent function and reliability. All parts are disassembled and put through a specialized hot wash tank heated to 198 degrees to ensure the casing and housings are pristine. We carefully inspect the casing for any flaws or fractures to ensure structural integrity. The hard parts undergo a meticulous inspection, and only those fit for duty are used. The rebuilding process includes a complete 10L1000 Overhaul Kit with all new seals, gaskets, and sealing rings. We specifically target the "D" clutch pack—engaged in 10 different gears—replacing the friction material with high-coefficient GPZ clutches to increase torque capacity well beyond factory limits.

Thorough Testing of the Valve Body and Entire Transmission Before Shipping

We here at Tier One take pride in every built 10L1000 transmission we manufacture for the Duramax trucks. To make sure that you get a transmission that's as tough as your truck, Tier One puts the valve bodies and pumps through rigorous modification and testing. Our Pro Loc Valve Body calibration decreases the pressure required to engage the regulator valve from 120psi to 80psi, resulting in quicker shifts and less heat generation. We also modify the lock-up circuit to decrease the time from apply to zero turbine slip, protecting the converter clutch. After final assembly of the transmission itself, we put it through a complete inspection to ensure proper tolerances.

Specifications:

• Vehicle fitment: 2020+ Chevy Silverado or GMC Sierra 2500HD/3500HD 6.6L Duramax
• Transmission Type: Allison 10L1000
• Power Rating: 800+ HP
• Transmission Pan: Deep Cast Aluminum (4 quarts over stock)
• Valve body: Pro Loc Modified Valve Body & Pump
• Line Pressure: Increased up to 60psi over stock
• Lube Pressure: Increased to 20psi (250% increase)
• Clutches: Raybestos Powertrain GPZ Frictions
• "E" Clutch Drum: High Capacity with Billet 6061 Apply Piston & 4140 Steel Dowels
• "F" Clutch: Upgraded to 5 clutches (25% more capacity)
• "D" Clutch: Upgraded with GPZ material
• CDF Drum: New OEM Assembly
• Trashcan: Hard Anodized New OEM F Clutch Cylinder
• Filters: New Pan Filter included

Tuning Notes:

• For maximum results in power levels exceeding 800HP, it is highly recommended that the TCC (Torque Converter Clutch) apply offset be changed in the factory file calibration.
• This transmission is designed to work with increased line pressures provided by the mechanical pump upgrades; however, custom tuning is recommended to fully utilize the quicker shift timing and lock-up characteristics.

2-Year, Unlimited Mile Warranty: each Tier One built transmission comes backed by a 2-year, unlimited mile warranty. Please see our Warranty Terms and Conditions here.

Transmission Break-in: in order to maintain your warranty, this transmission requires a 300-mile break-in and a relearn process.

Core charge: this transmission includes a core charge that will be refunded once Tier One receives your stock transmission, inspects it, and finds it in acceptable condition. The core charge can be fully or partially waived if you send in or drop off your stock transmission ahead of time.

Freight Shipping: this transmission ships via freight. Please carefully inspect your transmission before signing your Bill of Lading. If your transmission arrives damaged, please call us directly at 602-399-5484.