Allison 10-Speed (10L1000) Automatic
Type
Automatic
Speeds
10
Years
2020-2026
Builder
Allison Transmission / General Motors
Paired with: Chevrolet/GMC 2500HD-3500, Duramax L5P (2020 onward)
Simplified torque-flow diagram — where this transmission sits in the drivetrain, not a literal cutaway of its internals.
Developed for the L5P Duramax and built by GM (at its Toledo Transmission plant) rather than by Allison directly, despite carrying the Allison name. It has the highest relative torque capacity of any transmission in this class to date, exceeding rivals like the Aisin AS69RC or Ford's 6R140.
Strengths
- Highest relative torque capacity of any transmission in its class to date, engineered specifically for the increased power and torque of the modern L5P.
Known weaknesses
Torque converter lockup mechanism failure is one of the most frequently reported issues, especially with increased horsepower, larger tires, or heavy towing.
Note: Keep modifications modest on a stock converter, or upgrade the converter for heavier use.
Valve body failures and long repair times have been reported, including a documented recall affecting 2020-2022 model-year trucks.
Note: Check recall status on any 2020-2022 truck.
Performance tuning and emissions deletes push the clutch packs and friction elements beyond their factory-power design limits, leading to burnt clutches and slipping.
Note: Emissions-delete tuning is also illegal to perform on a vehicle originally so equipped; use only compliant tuning within factory power levels.
Sources
- Allison 10L1000 Transmission, Problems, Solutions & Upgrades (NextGen Diesel) (accessed 2026-09-22)
- Allison 10L1000: Specs, Problems and Upgrades (Alligator Performance) (accessed 2026-09-22)