February 21, 2013
The actuator feed limit (AFL) valve in GM 4L80-E and 4L85-E units has a large reaction area and is greatly affected by side loading, which wears the valve body bore. The EPC solenoid oscillates the torque signal and AFL oil, which increases valve action and accelerates wear. As bore wear increases, oil pressure is reduced to the shift solenoids, which causes solenoid and ratio codes. The same AFL oil loss results in lower line pressure.
Installing Sonnax actuator feed limit valve kit 34200-16K corrects AFL oil pressure loss, restoring shift solenoid pressure to prevent wrong gear starts and other shift concerns. The hard-coat anodized valve is extremely wear resistant, and annular grooves have been added to minimize the effect of side loading. The Sonnax wear-resistant sleeve provides more valve contact area, providing additional support and further reducing valve and bore wear.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.