Sonnax

About Sonnax: Drivetrain Innovation Since 1978

Sonnax has been setting the standard for transmission and drivetrain excellence since its founding in 1978. Headquartered in Bellows Falls, Vermont, the company has grown from a specialized domestic supplier into a globally recognized authority on automatic transmission, torque converter, and driveline components. Today, Sonnax Transmission Company operates as a Marmon/Berkshire Hathaway company, with production facilities and technical development centers spanning multiple states and a distribution network that reaches more than 70 countries worldwide.

Engineering Philosophy: Fix the Root Cause

What truly distinguishes Sonnax in the aftermarket is its engineering philosophy. Rather than simply replacing worn components with like-for-like copies, Sonnax engineers investigate the underlying causes of transmission and converter failures. By combining new materials, innovative geometries, and rigorous state-of-the-art testing, the company consistently delivers parts that don't just restore OE performance — they often improve upon it. This approach has earned Sonnax repeated recognition in Transmission Digest’s annual Top Products awards, with readers — working transmission professionals — voting Sonnax products among the best in the powertrain aftermarket year after year.

The World’s Largest Full-Line Torque Converter Supplier

Sonnax holds a unique distinction: it is widely recognized as the world’s largest full-line supplier of torque converter parts. From friction rings and damper hubs to clutch plates and turbine components, the catalog covers an extraordinary breadth of makes and models. That same depth of coverage extends to automatic transmission hardware, where Sonnax offers everything from individual valves and sleeves to complete automatic transmission valve body kits and fully remanufactured automatic transmission valve bodies.

Valve Body Expertise & Zip Kit® Technology

The valve body is the hydraulic control center of any automatic transmission, and Sonnax has invested heavily in understanding every aspect of its failure modes. Their proprietary Zip Kit® technology allows rebuilders to address the most common wear points in a valve body with precisely engineered drop-in components, minimizing labor time without sacrificing quality. For shops and rebuilders who need a comprehensive solution, Sonnax also offers automatic transmission valve body overhaul kits that bundle critical components together for a thorough, efficient rebuild.

Clutch Components Built for Durability

Beyond valve body solutions, Sonnax produces a respected line of automatic transmission clutch housings and related clutch components. These parts are engineered with the same root-cause philosophy — for example, utilizing lightweight housings with steel inserts to eliminate chronic clutch wear, or employing high-strength steel hubs ideal for both stock replacement and performance-oriented rebuilds. Coverage spans a wide range of popular domestic and import transmission platforms.

Technical Support That Sets the Standard

Sonnax doesn’t just sell parts — it educates the industry. The company maintains an extensive library of free technical articles, instructional guides, and diagnostic resources available around the clock on its website. This commitment to knowledge-sharing has made Sonnax an indispensable partner for independent transmission shops, fleet rebuilders, and performance enthusiasts alike. With more than four decades of proven expertise and a product catalog of hundreds of SKUs covering virtually every major automatic transmission platform, Sonnax remains a first-call brand for professionals who demand precision.