The invention relates to a non-permanent drive device consisting of two gear wheels (4a, 4b) which can be coupled to a primary shaft (1) by means of a clutch mechanism including at least two cones (3a, 3b) mounted so that they can slide freely and kinematically attached, in terms of rotation, to the shaft (1), the said cones interacting with a tapered bearing surface (15) of the wheel. According to the invention, the gear wheels (4a, 4b) are held kinematically attached in terms of rotation by penetration of at least one tooth (16) overhanging in a projecting way from the front face of at least one of the wheels into a gap of complementary shape of the front face of the wheel facing it so as to maintain permanent contact between the said wheels without slack in an engaged position. Application: gearboxes <IMAGE>
