Sonnax Smart-Tech drum module 34555-01K for racing GM TH400 transmissions improves on-track performance and consistency, leading to quicker ETs, more wins and greater reliability.

The TH400 is preferred for its overall durability and multitude of available ratios, but is known to be heavier and less efficient than the popular two-speed Powerglide. Part of the TH400 inefficiency results from the fact that the direct drum counter rotates, spinning backwards in 1st Gear, brakes to a complete stop on the 1-2 shift, then goes from 0 RPM to input RPM on the 2-3 shift. Significant energy is wasted through this cycle that robs power, upsets traction on the shifts and contributes to broken internal parts.

Compared to aluminum direct drums, the Smart-Tech drum module reduces the weight of the counter-rotating components by over 3.3 lbs! And more significantly, because the weight of the Sonnax counter-rotating parts is closer to the centerline, there is a 53% reduction in energy required to stop and restart during the 1-2 and 2-3 shifts. The benefits are increased wheel horsepower, better acceleration, less shock on the shifts and improved durability.

• Complete kit replaces both forward and direct drums and includes everything from intermediate sprag to the pump; a selection of Sonnax input shafts is available separately
• 100% new content, no used core pieces
• Includes larger-diameter, 36-element sprag and sprag race that works with OE intermediate clutches
• Includes six-friction forward clutch pack and seven-friction direct clutch pack