- Servo Assembly
- Cover Gasket
- Case-to-Cover O-Ring
- Return Spring
- Servo Pin Seals (2) PTFE, 1 extra
- Primary Piston Seals (2) PTFE
$214.64 Each - Free Shipping
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.
What is the difference between 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.