Smart-Tech® Drum Module
Part No. 34555-01K

For racing applications that do not use front band.

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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
  • Forward Piston Housing
  • Forward Piston
  • Forward Piston Return Springs (16)
  • Forward Spring Retainer
  • Forward Snap Ring
  • O-Ring 1.674"
  • Lip Seals (2)
  • Direct Housing Assembly
  • Direct Piston
  • Direct Piston Return Springs (26)
  • Direct Spring Retainer
  • Direct Snap Ring
  • O-Ring 2.737"
  • Sprag Shaft
  • Front Sprag Retainer Plate
  • Heavy Duty Sprag 36 Element
  • Outer Sprag Race
  • Rear Sprag Retainer Plate
  • Sprag Retainer Screws (4) 6-32 x 5/16"
  • Quad Ring Seals (2)
  • Anti-rotation Seal Rings (2)
  • Drum
  • Pressure Plate
  • Outer Snap Rings (4)
  • Bearing Small
  • Forward Clutch Hub
  • Bearing Large
  • Direct Clutch Hub
  • Steel Clutch Plates (4) .060"
  • Steel Clutch Plates (11) .077"
  • Friction Clutch Plates (13) .080"
  • Clutch Separators (60) .103"

  • TH400 Smart-Tech® Drum Module 34555-01K
  • TH400 Smart-Tech® Drum Module 34555-01K details
  • TH400 Smart-Tech® Drum Module 34555-01K details
  • TH400 Smart-Tech® Drum Module 34555-01K details
  • TH400 Smart-Tech® Drum Module 34555-01K details
  • TH400 Smart-Tech® Drum Module 34555-01K details
  • TH400 Smart-Tech® Drum Module 34555-01K details


How to Assemble & Install the TH400 Smart-Tech Drum Module
Improve TH400 Performance, Consistency & Safety with the Smart-Tech Drum Module

They are fast. You can either run one or get beat by one.

Jeremy Jones
RPM Transmissions

All the claims are true, no hype. If you are the type of racer that is always seeking an edge, this is worth it in many different scenarios.

Steve & Dustin Trance
Hot Rod Drag Week Class Champions

This Smart-Tech module is as significant to the high performance transmission industry as the day Neil Armstrong said "That's one small step for man, one giant leap for mankind!" Thank you to everyone that contributed to this product!

L. Barnett