Allison 1000 Stock Plus

Factory Drivability. Enhanced Durability. Built to Work.

The Thompson Transmission Allison 1000 Stock Plus is designed for Chevrolet and GMC Duramax owners looking for a dependable transmission that delivers improved reliability without sacrificing factory drivability. Whether you're daily driving, towing heavy trailers, or hauling equipment, our Stock Plus build addresses common weaknesses in the factory Allison 1000 while maintaining smooth, consistent shifting.

Unlike a standard factory rebuild, our Stock Plus incorporates upgraded hydraulic components, improved C3 clutch oiling, and a heavy-duty torque converter to provide better durability under demanding conditions. Each transmission is carefully assembled with attention to clutch clearances, hydraulic integrity, and long-term reliability.

Key Features & Upgrades

• Performance Shift Improvement Kit – Enhances hydraulic control, clutch application, and shift consistency.

• Upgraded C3 Clutch Oil Covers – Improve oil management within the C3 clutch assembly to promote reliable clutch operation.

• Heavy-Duty Torque Converter – Designed for increased durability, dependable lockup performance, and reliable power transfer under load.

• Premium Clutches & Steels – Quality friction components designed for consistent engagement and long-term durability.

• Upgraded Seals & Gaskets – Help maintain hydraulic integrity and minimize internal pressure loss.

• Inspected & Serviced Valve Body – Evaluated for wear and hydraulic concerns to ensure dependable shift performance.

• Precision Clutch Clearance Setup – Each clutch pack is measured and assembled to proper operating specifications.

• Complete Internal Inspection – Critical hard parts, bearings, and bushings are inspected and serviced as needed.

• Optional Deep Transmission Pan – Available for customers looking for additional fluid capacity and improved thermal management.

Built for Everyday Reliability

The Allison 1000 is a proven heavy-duty transmission, but demanding towing conditions, excessive heat, and years of use can expose weaknesses in the factory hydraulic and clutch systems.

Our Stock Plus build focuses on improving these critical areas while preserving the smooth, predictable shifting characteristics expected from an Allison transmission.

With upgraded hydraulic controls, improved C3 clutch oiling, and a heavy-duty torque converter, the Stock Plus delivers the durability needed for daily driving and demanding work applications.

Thompson Transmission Allison 1000 Stock Plus — Built for the Load. Engineered for Reliability. Ready for the Long Haul.