Disclosed is a hydraulic control system including a hydraulic fluid source; line pressure control means for regulating hydraulic pressure supplied from the fluid source to line pressure; reducing pressure controller for reducing hydraulic pressure from the line pressure control means; range controller for selectively supplying hydraulic pressure from the line pressure controller; shift controller for supplying hydraulic pressure; hydraulic pressure controller for converting hydraulic pressure to operational pressure; and hydraulic pressure distributer for determining a hydraulic flow path according to the hydraulic pressure from the shift controller; wherein the hydraulic pressure distributer includes an end clutch valve supplying operational pressure to an end clutch; a low-reverse brake valve supplying operational pressure to a low-reverse brake; a first rear clutch valve supplying operational pressure to a rear clutch; a second rear clutch valve supplying hydraulic pressure to the first rear clutch valve; a 1-2 shift valve supplying hydraulic pressure to friction elements operating when 1-2 shifting; and a 2-3/4-3 shift valve supplying hydraulic pressure to friction elements operating when 2-3 and 4-3 shifting.

A control system for an automatic transmission having a transmission gear mechanism and a plurality of friction coupling elements which are selectively locked and unlocked with hydraulic oil to change power transmission paths to place the automatic transmission into desired available gears, a first one of the friction coupling elements having a locking pressure chamber and an unlocking pressure chamber and being locked when operating oil is supplied into only the locking pressure chamber and unlocking when operating oil is coincidentally supplied into the locking pressure chamber and the unlocking pressure chamber, and a second one of the friction coupling elements having a locking/unlocking pressure chamber in communication, with the unlocking pressure chamber of the first friction coupling element and being locked only when operation oil is supplied into the locking/unlocking pressure chamber. The control system includes a transition level control for controlling a pressure level of transitional pressure of operating oil increasing in pressure level while being supplied to the locking/unlocking pressure chamber of the second friction coupling element during a first specified gear shift with a first friction coupling element and the second friction coupling element are simultaneously unlocked and locked, respectively, and decreasing while being discharged from the locking/unlocking pressure chamber of the second friction coupling element during a second specific gear shift wherein the first friction coupling element and the second friction coupling element are simultaneously locked and unlocked, respectively, and a transitional duration control for controlling a duration time of the transitional pressure during any one of the first and second specific gear shifts.

A hydraulic control system of the present invention is provided for improving a responsiveness to a speed change by compleating the speed chang with a torque pressure control hydraulic pressure after initiating the speed change with the drive hydraulic pressure. The hydraulic control system includes an oil pump for generating hydraulic pressure, a pressure regulating valve for regulating the hydraulic pressure to be proper pressure for reverse and drive, five friction elements which receive the hydraulic pressure for drive in accordance with operation of a manual valve, two friction elements which receive the hydraulic pressure for reverse in accordance with operation of the manual valve, first and second shift control parts having at least two shift valves, respectively, to supply the hydraulic pressure to the friction elements, and a torque control hydraulic pressure regulating part for supplying a torque control hydraulic pressure to the first and second shift control parts.

A hydraulic control system of a vehicle automatic transmission includes a torque converter, an oil pump, a pressure regulator, a damper clutch working control means, a manual valve, an N-D control valve, a torque control regulator valve, a control switch valve, a first to second, second to third, third to fourth, and third to second shift valves, a low/reverse clutch valve, a third clutch valve, and a second to fourth brake valve.

Power transmissions incorporate gear ratios including a plurality of forward ratios, a neutral condition and at least one reverse ratio. The establishment of each ratio is controlled by selectively engageable hydraulically operated friction devices, such as clutches and brakes. The interchange between forward ratios is controlled by the interchange of at least one friction device. The control elements to accomplish the establishment and interchange of the ratios include a pressure source, shift valve, solenoid control valves and pressure control valves. The solenoid valves are electrically actuated and the hydraulic portion of the control includes elements that permit continued operation of the transmission in selected ratios in the event of electrical discontinuance. Also provided within the hydraulic control is a pressure knockdown or pressure reducing valve element which operates with one of the shift valves to establish a maximum pressure level in the forward ratios that is less than the maximum pressure level in the reverse ratio.