Super Hold Servo Kit
Part No. 28821-09K

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Sonnax super hold servo kit 28821-09K is an all-in-one upgrade ideal for a competitive edge in GM Powerglide applications where racers are looking to reduce line pressure to free up horsepower. The kit's dual piston design features 30% more apply area to increase band apply force at your current line pressure or allow you to reduce line pressure by 20% to 30% while maintaining the same apply force.

  • Dual piston design for 30% more apply area
  • Spring counteracts pin bias effect up to 275 psi
  • Improved sealing throughout
  • Low-profile design ensure adequate clearance
  • 6061 Anodized billet aluminum cover

A common question is, "I have an extreme application, how do I choose between the Sonnax Smart-Tech® servo and the super hold servo?"
Both are track-proven in today’s high-power vehicles. With its ratio-style release and supported pin design, the Smart-Tech 28821-10K is the best all-around upgrade that eliminates EVERY problem associated with the OE servo. Racers looking to reduce line pressure for greater efficiency will most benefit from the super hold servo’s 30% more apply area.

  • Servo Assembly
  • Cover Gasket
  • Case-to-Cover O-Ring
  • Return Spring
  • Servo Pin Seals (2) PTFE, 1 extra
  • Primary Piston Seals (2) PTFE

  • Powerglide Super Hold Servo Kit 28821-09K


Prevent "Mystery" Powerglide Band Failures by Overcoming the Servo Pin Bias Effect

Hands down your Powerglide super hold servo kit finally cured my problems I chased for months. Looking forward to making the switch this off season to your Smart-Tech drum.

T. Cannon
DoubleDown Performance