The GM 8L45 and 8L90 clutch control valves have an inboard valve spool fed by a hole through the valve into the casting. This design makes vacuum testing the inboard spool and casting by traditional methods impossible. Wear at the inboard valve spool allows clutch apply oil leakage, which diminishes the fluid force applied to the clutches, resulting in burnt clutches and poor shift quality.
The Sonnax clutch control valve vacuum test tool kit 154740-TL11 enables quick and easy vacuum testing of the inboard testing location. This tool can also be used to test the outboard location. If excessive wear is found, repair by installing Sonnax drop-in clutch control valve kit 154740-11K or 154740-13K.