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Powerglide

Race-Calibrated Servo Return Spring Kit

Part No.

28133-HD

OE Part No: 3830235, 3815914, 3830235

Race-Calibrated Servo Return Spring Kit
  • Race-Calibrated Servo Return Spring Kit

Small_28133-hd-in

Powerglide

Race-Calibrated Servo Return Spring Kit

Part No. 28133-HD

OE Part No: 3830235, 3815914, 3830235

  • Shims (2)
  • Spring

The servo return spring is the source of many "mystery" band failures caused by inconsistent servo release and weak springs prone to collapse. Sonnax race-calibrated servo return spring kit 28133-HD for Powerglide units ensures optimum servo function in high gear for longer band life, cooler transmission and tunability of shift.

Designed to overcome the pin bias effect, the Sonnax race-calibrated spring has higher seat pressure to help ensure full servo release, but with a lower rate for greater net apply force. Watch this video to see exactly how the servo performs at high pressures when fitted with an OE, light aftermarket or Sonnax race-calibrated spring.

  • Specifically designed to work with line pressures from 200 to 275 psi
  • Includes two .050” shims to aid in tuning at higher line pressures

Related Parts

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

Unexplained band failure in Powerglides is a common problem that can be overcome by understanding the servo pin bias effect. This video demonstrates how the servo performs at high pressures when fitted with an OE, light aftermarket or Sonnax race-calibrated spring, available as a standalone component or in Sonnax 28821-20K. The video dramatically shows the pin bias effect in action, and why overcoming this built-in design flaw of the Powerglide servo is the only way to prevent “mystery” band failures.

Learn more about the servo pin bias effect.

Contact a Sonnax Distributor to purchase this part.