Powerglide Supported Servo Master Kit 28821-20K
“Mystery” band failures are a common result of aftermarket servo return springs and weak OE springs prone to collapse that do not reliably release the servo. The Sonnax spring in this kit is race-calibrated 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.
- Unique cover and pin combination eliminates piston binding that causes unexplained band failure
- Race-calibrated spring counteracts pin bias effect up to 275 psi
- Dual PTFE seal rings for better seal and low friction
- OE apply area
- Low-profile design ensures adequate clearance
- 6061 Anodized billet aluminum cover