April 21, 2021
GM 8L45 and 8L90 units often suffer burnt clutches, shift concerns, low line pressure and/or converter apply complaints due to excess wear in the signal accumulator piston bores in the control solenoid valve body casting. This wear allows valuable VFS signal pressure to exhaust, preventing proper shift control, line pressure regulation and/or converter clutch apply.
Reconditioning these bores and installing Sonnax oversized signal accumulator piston kit 154740-01K re-establishes correct clearance for proper VFS signal pressure.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.