Pressure loss, a burnt 2-3-4-6-8 (S4) clutch and poor shift quality are common complaints with the GM 8L45 and 8L90 transmissions. These symptoms can be caused by a worn S4 clutch control valve and bore that allows valuable clutch apply fluid pressure to leak, reducing the force needed to apply the clutch. Sonnax S4 clutch control valve kit 154740-24K is a drop-in valve with an added scarf-cut seal at the signal apply end and a lengthened inboard spool at the clutch apply end that seals worn bores and restores proper hydraulic function.
Early-design valve bodies have a different design S4 valve. This Sonnax valve in this kit can not be used in the early S4 location.