This kit is intended for applications with aftermarket tuning that accommodates more aggressive clutch apply from additional friction and removal of waved plate. Installation in OEM calibrated vehicles may result in more pronounced shift feel during application of the 4-5-6 clutch.
GM 6L80 and 6L90 transmissions often suffer failure of the 4-5-6 clutch assembly due to OE design shortcomings. Not enough clutches and insufficient clutch piston-to-plate apply surface area causes clutch plate failure, especially when apply pressures exceed OE specifications. The other problem is flexing and bowing of the backing plate (coning), which is a primary source of clutch failure.
Sonnax high capacity 4-5-6 clutch apply piston kit 104960-10K features a modified OE clutch apply piston and piston dam that are used in conjunction with a specially-designed toothed apply plate closest to the piston. The Sonnax toothed apply plate increases surface area between the apply piston and first friction plate resulting in more even distribution of apply force to clutch plates and allows a friction plate to run against the apply plate. By eliminating the OE waved plate and adding one additional OE-thickness friction, 4-5-6 clutch capacity is increased by 17%, resulting in a 4-5-6 clutch pack that can handle modified engines with increased power output.
OEM frictions are about .063" thick, and OEM steels are about .086" thick. Utilizing these frictions and steels, this kit allows one additional friction plate to be installed for a total of 7 frictions in a 6L80 and 8 frictions in a 6L90.