Abstract: A flywheel comprises first and second members disposed on the sides of an engine and a transmission and rotatable relative to each other; a sealed chamber disposed between the first and second members and filled with a viscous fluid; a plurality of resistance plates disposed within the sealed chamber and alternately engaged with the first and second members; a detector for detecting a drive torque transmitted from the engine through the flywheel to the transmission; and a device for engaging the first and second members with each other based on the detection of the drive torque by the detecting means. The flywheel may comprise an operating device for increasing a torque transmitted between the resistance plates based on the detection of the drive torque by the detector.