GM Gen. 2 6T70/75/80 units often suffer shift abnormalities caused by excess wear in the actuator feed accumulator piston bores. This wear allows actuator feed limit fluid loss which prevents proper regulation of oil pressure supplied to control solenoids, resulting in harsh or soft shifts, solenoid codes and clutch failure.
Reconditioning the bore and installing Sonnax oversized actuator feed accumulator piston kit 124740-65K re-establishes correct clearance for revived shift control in all ranges.
Original release 124740-TL40 works in Gen. 1 only. To update to work in Gen. 2 applications requires purchase of jig plate 124740-JP40.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.