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Race-Calibrated Servo Return Spring Kit
Part No. 28133-HD

OE Part No. 3830235, 3815914, 3830235

View Instructions

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
  • Shims (2)
  • Spring

April 27, 2016

Understanding & Overcoming the Powerglide Servo Pin Bias Effect - Part 1

Topics: Diagnostics And Theory Transmission GM Powerglide Transmission

Read Now

April 26, 2016

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

Topics: Diagnostics And Theory Transmission GM Powerglide Transmission

Watch Now
  • 28133 hd in