Burnt clutches and poor shifts are common issues with GM 8L45 and 8L90 transmissions. These issues can be caused by worn clutch control valves bores allowing valuable clutch apply fluid pressure to leak, reducing the force needed to apply the clutches. Sonnax S1/S5 Clutch Control Valve Kit 154740-13K is a drop-in valve with an added seal at the signal apply end and lengthened inboard spool at the clutch apply end that seals worn bores and restores proper function.
Sonnax bore sizing tool 154740-BST13 may be needed to ensure proper clearance between the valve and bore.
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. Outboard ports should be checked with solenoid installed. Inboard ports require solenoid removal and [154740-TL11] tool and can only check the OE valve.