Patent ID: 7258212

Claim:
An automatic transmission of a vehicle comprising: multiple oil pressure control valves to be connected to multiple friction engagement elements for controlling an oil pressure of a working oil to be supplied to the respective friction engagement elements, so that each of the friction engagement elements is engaged or disengaged depending on the oil pressure applied thereto; a line pressure generating means for generating a line pressure; multiple pressure modulating valves to be connected to the line pressure generating means for modulating the line pressure of the working oil to be supplied to the oil pressure control valves; and a switching valve provided between the pressure modulating valves and the oil pressure control valves, wherein the switching valve is connected to all of the oil pressure control valves through an oil pressure supply passage, and wherein the oil pressure supply passage is operatively connected to one of the pressure modulating valves the oil pressure from which is at a normal operating pressure, whereas the oil pressure supply passage is operatively disconnected from the other pressure modulating valve the oil pressure from which is lower than the normal operating pressure, when a pressure difference between the oil pressures from the pressure modulating valves becomes higher than a predetermined value.