Sonnax has introduced a new drop-in S4 clutch control valve kit for GM 8L45 and 8L90 transmissions. Sonnax says users can replace worn parts with this kit (part no. 154740-24K) to restore proper hydraulic control and renew clutch apply fluid pressure performance.
The company notes that the Sonnax valve in this kit cannot be used in the early S4 location, as early-design valve bodies have a different design S4 valve.