January 21, 2013
This kit does not address wear on the inboard two spools. To address wear in that location, use Sonnax oversized 4-3 sequence valve kit 77964-14K.
GM 4L60-E, 4L65-E and 4L70-E transmissions often have trouble shifting into or holding 4th Gear due to excess wear in the sequence valve bore. This wear allows vital 4th Gear accumulator oil to exhaust, resulting in deficient servo apply pressure. Consequences are slipping or no 4th Gear operation followed closely by a burnt band. Leaking at the OE end plug also allows oil loss that can leave 4th Gear inoperable. Re-establish hydraulic control and restore normal operation by reconditioning the bore and installing Sonnax oversized 4-3 sequence valve kit 77964-04K.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.