6L80/6L90 4-5-6 Clutch Apply Piston kit
GM 6L80 and 6L90 transmissions often suffer failure of the 4-5-6 clutch assembly due to OE design shortcomings. Insufficient clutch piston-to-plate apply surface area causes clutch plate failure, especially when apply pressures excede OE specifications. The other problem is flexing and bowing of the backing plate (coning), which is a primary source of clutch failure.
The Sonnax apply ring increases surface area between the apply piston and the OE waved clutch plate, resulting in more even distribution of apply force to the clutch plates. The Sonnax backing plate minimizes flexing/bowing when clutch is applied, drastically reducing the likelihood of clutch plate distortion.