Aluminium Case Powerglide

Mystery band failures in GM Powerglides are a common result of using inconsistent aftermarket servo return springs and weak OE springs prone to collapse. This is a problem that can be traced directly to the pin bias effect. This Sonnax race-calibrated servo return spring kit counteracts pin bias effect to ensure consistent servo function for longer band life and a cooler transmission. The spring's higher seat pressure helps ensure full servo release, but also features a lower spring rate to prevent excessive release force in the apply position.

Watch the video to see exactly how an OE servo performs at high pressures when fitted with an OE, light aftermarket or Sonnax race-calibrated spring.

• Counteracts pin bias effect up to 275 psi
• Includes two .050” shims to aid in tuning at higher line pressures
• Works with both OE and aftermarket servo pistons

Contents:

• Shims (2)
• Spring

SONNAX Installation Instructions

Sonnax Race-Calibrated Servo Return Spring Kit - 28133-HD