The Sonnax mission is to be the leader in bringing innovative, high-quality drivetrain components to the automotive aftermarket.

Sonnax Transmission Company is an industry leader in the cutting-edge design, manufacture and distribution of the highest quality products to the automotive aftermarket, commercial vehicle industries and industrial sectors utilizing drivetrain technology. Sonnax Transmission Company, a Marmon/Berkshire Hathaway company, serves the aftermarket with both the Rostra Powertrain Controls and Sonnax brands.

After decades of serving the transmission aftermarket as standalone companies, Sonnax and Rostra Powertrain Controls integrated in 2021 to become a single, transmission-focused organization.

What sets us apart from the competition is our passion for quality and innovation. This passion exhibits itself in our long-standing philosophy to address the root cause of a problem, and not just treat the symptoms. In striving to discover what causes common transmission and converter problems, we meld new ideas, materials and state-of-the-art testing to ensure our parts will restore OE performance, or make it better-than-new.

Sonnax Transmission Company headquarters is in Bellows Falls, Vermont, with production facilities in Laurinburg, N.C. and technical development centers in California, Georgia, Indiana, Missouri and Wisconsin. We proudly hold ISO:9001 2015 certification for our Quality Management System.

Our Brands

Sonnax designs, manufactures, tests and distributes a wide variety of components used to remanufacture torque converters, rebuild automatic transmissions, upgrade driveshafts and protect the driveline from over-torque damage.

As a leading supplier to the automotive aftermarket, Sonnax exports to more than 70 countries and supports emerging markets worldwide. An international network of distributors, remanufacturers and technical resources is one result of our commitment to successful partnerships with our customers.

After more than 40 years in business, the Sonnax name has become synonymous with quality parts, outstanding service and technical expertise that are second to none.

Rostra Powertrain Controls is a leading manufacturer and distributor of OE and aftermarket powertrain electronics. Product specialties include solenoids, sensors, switches, wire harnesses and modulators.

With more than 30 years of experience in the automatic transmission parts arena, Rostra Powertrain is recognized globally for exceptional quality and customer service. For more information on Rostra products, please visit


To be the leader in bringing innovative, high-quality drivetrain components to the automotive aftermarket.

To achieve our mission Sonnax is focused on three broad strategies:

  • Identify, develop and deliver products to meet strict design and manufacturing standards in a timely fashion
  • Provide excellent customer service through technical support, education and friendly customer response
  • Provide our employees with a rewarding career experience that is respectful and challenging

True collaboration toward a common goal is not something you see everyday, but that is what the Sonnax TASC Force is all about.

The Sonnax Technical Automotive Specialties Committee (TASC) Force is composed of experienced transmission rebuilders and technicians who value technical innovations and have hands-on understanding of the latest units and industry developments. From around the globe, the best minds in the transmission industry willingly share their know-how, with the understanding that everyone benefits when good ideas and products emerge from centuries of combined transmission wisdom.

Independent TASC members work for large shops, small shops, volume transmission and volume valve body rebuilders. Alongside Sonnax engineers and specialists, they are helping to develop repairs which will be used by their companies and by the rest of the transmission aftermarket.

TASC Force members contribute product ideas, test new products, troubleshoot results, and get together on a regular basis to listen, discuss and compare findings. Their efforts help provide answers and repairs for the entire industry. Everybody wins.

This website and all of its contents are the intellectual property of Sonnax Transmission Company, Inc. No portion of this work may be reproduced or transmitted in any form or by any means, mechanical or electronic, including photocopying and/or recording, or by any other information storage and/or retrieval system without the prior written consent of Sonnax Transmission Company, Inc. Sonnax customers may use the part numbers only for the limited purpose of placing orders with Sonnax or otherwise operating their business, but in no case is permission granted to any customer, business entity, or individual to utilize the part numbers in order to compete with Sonnax.

Data Collection/Usage

Sonnax Transmission Company uses the personal information that it collects to provide you with information about our products and services. The Sonnax website collects the following data:

How We Get the Data What Data Why?
Automatically Data about which pages you visit on the Sonnax website and information from your browser such as your anonymized IP address. In order to analyze content performance and optimize the Sonnax online experience. This information also helps with troubleshooting errors.
User Submitted Contact Information & Consumer Communications The website allows you to request information from Sonnax. Website forms collect your information so we receive feedback and answer questions.
User Submitted Email Address & Preferences Users can opt-in to receiving email communications from Sonnax.

Sonnax takes data security seriously and maintains electronic and procedural safeguards to help protect your personal information. However, no system is 100% secure. In the event of a data breach, we will notify all those affected.

Third Party Disclosure

Sonnax does not sell, share or rent your data. We use the below third-party services to store and utilize your data solely for the purposes outlined above.

Service Reason
Google Analytics To understand how users use the website. Only automatically collected data is sent.
Hotjar To understand how users use the website. Only anonymously collected data is sent.
Sendinblue Marketing Platform For email marketing.


Consent is required for Sonnax Transmission Company to process your personal data. By using this website, and interacting with Sonnax via Facebook, you give Sonnax permission to process your personal data for the purposes outlined in this policy.

You may withdraw consent at any time by contacting Sonnax, at which time your personal information will be removed. You may ask to see what personal data we hold about you and be provided with a summary of such personal data and the details of the purpose for which it is being processed.

Sonnax warrants to the purchaser that each part manufactured or supplied by Sonnax will be free from defects in material or in factory workmanship. The warranty period shall extend for six (6) months from the date of sale. Sonnax must receive all warranty claims before the end of the warranty period.

If Sonnax determines that the part is defective in material or in factory workmanship, Sonnax will, at its option, repair or replace the defective part, or issue an account credit for the purchase price. This remedy is Sonnax's sole liability and the sole remedy provided by Sonnax for any breach of warranty.

All warranty returns must be pre-approved. Please contact Sonnax if you have a part to be returned under this warranty.

This limited warranty does not cover any product, parts or systems that we do not manufacture or sell, nor any damage due to: (a) transportation; (b) storage; (c) mishandling, tampering, neglect, accidental damage, use, or misuse that is improper or for any purpose other than that authorized by Sonnax; (d) failure to follow the Product instructions; (e) installation not in accordance with Sonnax’s recommended installation guidelines; (f) failure to perform any preventive maintenance; (e) unauthorized repair; (f) modifications; (g) normal wear and tear; or (h) external causes such as accidents, natural disasters, abuse, or other actions or events beyond our reasonable control. Regular, routine maintenance to keep each Product in proper operating condition is not the responsibility of Sonnax.

This warranty is the only warranty applicable to parts manufactured or supplied by Sonnax, and is expressly in lieu of any other warranties, expressed or implied, including any implied warranty of merchantability or fitness for a particular purpose. Any representations or descriptions in brochures, ads or catalogs are approximate only and will not create any warranty or other obligation by Sonnax. There are no warranties which extend beyond the description on the face hereof.


Remanufactured Valve Body Limited Lifetime Warranty

All Sonnax remanufactured valve bodies are backed by a limited lifetime warranty. During the first year, defective valve bodies will be replaced, free of charge. After the first year, valve bodies may be returned for repair or replacement, with the only cost to the customer being shipping charges.

Warranty claims must be directed to Sonnax product support within 30 days of your knowledge of a potential defect and before any attempt is made to return a valve body. Failure to call before returning may result in a restocking fee.

Any unauthorized repairs, alterations, misuse or disassembly will void the warranty. Proof of purchase may be required.

Installation of a Sonnax valve body for diagnostic purposes will void the warranty; valve bodies subjected to such misuse and returned under warranty will receive core credit only.

No vendors without appointment.

Careers at Sonnax


Transmission Digest Top 10 Products Award

47-Time Winner

Transmission Digest Top 10 Tools Award

26-Time Winner

Best Places to Work in Vermont

2-Time Winner

Jasper Supplier Service Award

5-Time Winner

Governor's Worksite Wellness Award

6-Time Winner

ATRA/Gears Magazine Distinguished Supplier Award

TCRA Exporter of the Year Award

TCRA Appreciation Award