In second generation GM 6T70/75/80 units, AFL valve bore wear results in low pressure at the shift and control solenoid valve assembly. The OE valve has a large reaction area and is highly affected by side loading, which wears the valve body bore. As the bore wear increases, oil pressure is reduced to the shift solenoids, which causes solenoid and ratio codes. This also results in lower line pressure.
Reconditioning the bore and Installing Sonnax oversized AFL valve kit 124740-48K will restore hydraulic control to the shift solenoids.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.