Oversized Throttle Valve

Oversized Throttle Valve A low throttle boost condition is a common complaint in vehicles with a 700-R4 transmission. This loss of throttle boost oil creates poor line rise and accelerates 3-4 clutch and band failure. In late-model transmissions, the hardened steel throttle valve continuously oscillates in the cast iron valve body bore and eventually wears the three bore diameters. This wear allows throttle valve feed oil to leak past the valve spool and exhaust, resulting in a low throttle boost condition. This excessive leakage can be eliminated by installing the oversized Sonnax replacement throttle valve 77968. Required tool: 77968-RM NOTE: Not compatible with early '82-'90 aluminum sleeve units. It is necessary to use Sonnax reamer 77968-RM to re-qualify worn valve body bore.