April 21, 2021
Pressure loss, a burnt 2-3-4-6-8 (S4) clutch and poor shift quality are common complaints with 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. The Sonnax oversized S4 clutch control valve kit 154740-26K has an added scarf-cut seal at the signal apply end and a lengthened inboard spool at the clutch apply end that seals a reconditioned bore and restores proper function.
Sonnax "F-Tool" kits designed to service a specific bore require the VB-FIX, a self-aligning valve body reaming fixture. More information and instructions can be found online at www.sonnax.com.
Sonnax valve body layouts provide a detailed overview of individual units making it quick and easy to determine what’s available for the specific valve body you’re working on. See all Sonnax valve body layouts.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.