Abstract: A shift control system can perform clutch-to-clutch shifts without occurrence of delay in shifting operation and aggravation of shift shock, by decreasing an engaging force of a first frictional engagement device and increasing an engaging force of a second frictional engagement device, and comprises a low pressure retention instructer for maintaining the second frictional engagement device at a predetermined low level until a revolution speed of a rotary member reaches a predetermined value upon the shift, an engagement instructer for increasing the engaging force of the second frictional engagement device after the revolution speed of the rotary member has reached said predetermined value, and a pressure rise instructer for increasing the engaging force of the first frictional engagement device after increasing the engaging force of the second frictional engagement device.

Abstract: An oil pressure controller of an automatic transmission which is capable of supplying engaging pressures to hydraulic servos of two frictional engaging elements which require different engaging pressures by a single pressure governing valve with a good pressure governing accuracy. The oil pressure controller comprises a hydraulic power source (10), hydraulic servos (70 and 80), signal pressure generating means (20), a pressure governing valve (30) for governing an oil pressure (P.sub.s) from the hydraulic power source (10) by a signal pressure (P.sub.ACC) and a control valve (40). The pressure governing valve (30)has a pressure receiving face A.sub.1 to which the signal pressure is applied, a pressure receiving face A.sub.2 to which the engaging pressure (P.sub.s) is fed back in the opposite direction and a pressure receiving face (A.sub.