APPARATUS FOR CONTROLLING PRESSURE REDUCTION OF FRICTIONAL COUPLING DEVICE TO SHIFT DOWN AUTOMATIC TRANSMISSION OF MOTOR VEHICLE

An apparatus for controlling an automatic transmission of a motor vehicle, wherein a shift-down action of the automatic transmission is achieved with a releasing action of a hydraulically operated frictional coupling device, the apparatus including a rapid pressure reduction device operated upon determination that the shift-down action should be effected, for rapidly reducing a pressure of the frictional coupling device to a predetermined pressure level higher than a critical level at which the frictional coupling device starts slipping, an input torque determining device for determining an input torque of the automatic transmission, or a rate of increase of the input torque, and a rapid pressure reduction amount determining device for determining the predetermined pressure level to which the pressure of the frictional coupling device is reduced, on the basis of the input torque or the rate of increase thereof of the automatic transmission determined by the input torque determining device. The predetermined pressure level is preferably compensated based on a delay time between moments of decision and initiation of the shift-down action.