In Toyota U760E/F transmissions, the B1 brake clutch is applied in 2nd and 6th Gears. The B1 apply control valve redirects line pressure to the brake clutch. Wear at the valve and/or boost valve and sleeve can cause improper valve function, and in extreme cases, reduction in line pressure. Reaming the bore and installing the Sonnax oversized B1 apply control valve kit 47740-44K will control line pressure losses and restore valve function.
Vacuum testing at the port(s) indicated fails to hold the recommended minimum in-Hg, or if wear is visually detected.