PURPOSE: To eliminate variation of the transmission characteristic caused by change in the spool position and its locating error, when different transmission characteristics are to be obtained through movement of the spool, which is of variable throttle type installed on the discharge side in a drive coupling device for four-wheel driving utilizing an oil pressure pump.

CONSTITUTION: Two different places in axial direction of a spool chamber 60 accommodating No.1 and No.2 spool 61, 61 are put in communication with the discharge side of a vane pump 3 through a pair of communication holes 54, 55, in which throttle members 54a, 55a are fitted. The No.1 spool 61 opens one of the communication holes 54 when current feed to a drive coil 7 is shut off, moves through the action of a weak magnetic field associate with feeding of a minor current, and is detained at the backmost in the spool chamber 60. Thus No.1 communication hole 54 is closed. The No.2 spool 62 blocks the other communication hole 55 when the current feed to the drive coil 7 is shut, moves through the action of a strong magnetic field associate with feeding of a major current, and runs against the No.1 spool 61 to be deteined there. Thus No.2 communication hole 55 is opened. Different oil passage resistances in these throttle members 54a, 55a fitted in the communication holes 54, 55 give transmission characteristics in three different ways.