Abstract: The invention relates to a synchronous coupling with a straight-toothed coupling hub, a coupling star which is axially displaceable in relation thereto and is in engagement therewith. A synchronizing sleeve is held axially in the coupling star and is in engagement with it through ratchet teeth. The sleeve is in engagement with an output shaft for axial displacement thereon through a course thread wherein locking teeth on a locking sleeve can be brought into engagement with corresponding locking teeth on the coupling star. Screw-in teeth are provided at the driving shaft side and at the coupling star side. For the transmission of torque without problems in both directions of rotation, the locking sleeve is provided in engagement with the output shaft for axial adjustment thereon via adjusting teeth through a predetermined axial stroke relative to the driving shaft for interlocking the locking teeth together.