PURPOSE: To permit automatic coasting run and operation of engine brake and facilitate operation by permitting connection and disconnection of a clutch to be controlled electromagnetically by the operation of an accelerator pedal, brake pedal, and a changer lever.

CONSTITUTION: A clutch hub 5 is fitted into the sleeve 3 fixed on a drive pinion shaft 1 in slidable way, and the flange yoke 2 fixed to a propeller shaft 11 is rotatably fitted onto the shaft 1 described the above, and a synchro gear 6 is fixed to the yoke 2. The clutch hub 5 and the gear 6 are engaged through function of a spring 8, and disengaged by a magnet J through a fork 9, thus permitting connection and disconnection of the driving force. Excitation of the magnet J is performed through the operation of a brake pedal E, accelerator pedal G, and a change lever C. In other words, when the lever C is set at the top gear, and neither of pedals E and G is stepped-in, each of corresponding contact D, F, H, is closed, and the magnet J is excited, and then the hub 5 and the gear 6 are disengaged, and coasting run is maintained.