Abstract

A hydraulic controller for an automatic transmission, having a band brake having a large stopping force based on a self-boosting effect against rotation in a self-binding direction and having a comparatively small stopping force against rotation in the unbinding direction, a modulator valve for producing a modulator pressure by reducing a line pressure, a band brake hydraulic servo having a brake engaging hydraulic chamber and a brake releasing hydraulic chamber. A line pressure is supplied to the band brake hydraulic servo to stop rotation in the self binding direction when a predetermined transmission speed is selected. The line pressure is also supplied the band brake hydraulic servo to stop rotation in the unbinding direction when another transmission speed is selected. A modulator pressure is supplied to the brake engaging hydraulic chamber to stop the rotation in the self-binding direction of the band brake and to allow the rotation in the unbinding direction when an intermediate speed is selected. The risk of any shift from the predetermined speed to another speed via the intermediate speed is eliminated, thereby enabling the transmission to be shifted always correctly while reducing shift shocks.