Sonnax Smart-Tech® Forward Clutch Drum

Sonnax Smart-Tech® Forward Clutch Drum

Transtar Industries & Sonnax

Transtar's community of suppliers represents the most trusted and experienced in the industry. Sonnax shares our vision and meets the premium standards we set for all of our product offerings. We rely on the best aftermarket and OE suppliers in the industry. 

For Ford Applications: 4R70E, 4R70W, 4R75E, 4R75W, AODE:

Transtar Cleaning Products

A common failure of listed Ford transmissions is cracking of the forward drum at the snap ring groove. The manufacturing process of the OE snap ring groove creates high-stress points around the circumference of the drum. The drum is active in 1st, 2nd and 3rd gear ranges and suffers the most abuse on a forced 4-3 kick down when it reapplies at higher pressure. (Learn More)
The concurrent pressure from the forward clutch piston combined with the high stress at the snap ring groove causes the upper portion of the drum to split and separate at the groove. Depending on severity of crack, this can result in no forward engagement or slipping in 1st, 2nd and 3rd gear. The forged, one-piece construction of the Sonnax Smart-Tech forward clutch drum (Part #: S76554D) eliminates weakness at these stress points.
  • Increased groove depth for additional ring support
  • One-piece forged material provides increased strength and durability over the OE stamped drum.



  • OE forward clutch drum commonly splits at the snap ring groove creating no or slipping forward clutch apply. Restore proper gear engagement and hold by installing this sturdier, forged Sonnax forward clutch drum.

  • Beginning March 1, 2019 Sonnax will stop inserting instructions into their packaging of approximately 1,000 products.

    This change will primarily impact parts such as end plugs, valve kits and bushings that come in small bags. In general, instructions will continue to ship with larger components and boxed products such as Zip Kits® and The Sure Cure® kits.

    Instructions for all products will remain available on the Sonnax website. To ensure everyone has quick access to those documents, Sonnax created a simple search tool found at