Abstract: An automatic transmission includes six forward speeds and a reverse speed and includes first and second clutches, first, second, and third brakes, and first, second, and third planetary gear sets. An oil pressure control system of the transmission includes a first clutch and second brake controller allowing the first clutch to receive a fastening pressure in fourth, fifth, and sixth speeds, allowing the second brake to receive a fastening pressure in first speed and reverse, and allowing an operation state of the first clutch to be sustained upon operation of the first clutch; a second clutch controller allowing the second clutch to receive a fastening pressure in third and fifth speeds and reverse; a first brake controller allowing the first brake to receive a fastening pressure in second and sixth speeds; and a third brake controller allowing the third brake to receive a fastening pressure in first through fourth speeds.

Abstract: A pressure control system of an automatic transmission includes a control-pressure regulating valve, a path switching valve, and a coupling-pressure regulating valve. The path switching valve selectively outputs a control pressure or a line pressure, so that the coupling-pressure regulating valve regulates a coupling pressure based on the control pressure during gear shifting, and regulates the coupling pressure based on the line pressure after completion of the gear shifting.

Abstract: A hydraulic control system of an automatic transmission that precisely control is operating hydraulic pressure supplied to a frictional element during shifting and can eliminate oil leak under a maximum operating hydraulic pressure. The hydraulic control system controls a hydraulic pressure generated by a hydraulic pump to from an operating hydraulic pressure for a frictional element selectively operating at each shift ratio. A hydraulic line is configured such that the operating hydraulic pressure of the frictional element is controlled by a pressure control valve and a switching valve that are controlled by a solenoid valve. An exhaust hydraulic line of the pressure control valve is connected to an exhaust hydraulic line of the switching valve such that the exhaust hydraulic line of the pressure control valve can be controlled by a switching of the switching valve.

Abstract: An automatic transmission includes six forward speeds and a reverse speed and includes first and second clutches, first, second, and third brakes, and first, second, and third planetary gear sets. An oil pressure control system of the transmission includes a first clutch and second brake controller allowing the first clutch to receive a fastening pressure in fourth, fifth, and sixth speeds, allowing the second brake to receive a fastening pressure in first speed and reverse, and allowing an operation state of the first clutch to be sustained upon operation of the first clutch; a second clutch controller allowing the second clutch to receive a fastening pressure in third and fifth speeds and reverse; a first brake controller allowing the first brake to receive a fastening pressure in second and sixth speeds; and a third brake controller allowing the third brake to receive a fastening pressure in first through fourth speeds.