Abstract: A synchronization mechanism, especially for change-speed transmissions of motor vehicles, in which a shifting sleeve provided with shifting teeth is being held by a shifting sleeve carrier fixedly arranged on a transmission shaft and is adapted to be coupled--against the action of at least one friction member producing synchronism--with a coupling member of the gear to be shifted or engaged which is provided with shifting teeth; the friction member thereby consists of a slotted and springy synchronizing ring cooperating directly with the shifting teeth of the shifting sleeve which advantageously is under the influence of means increasing the servo-effect thereof; the end surface of the shifting teeth of the shifting sleeve are so constructed that the friction members become again ineffectual after the synchronizing operation is completed before the shifting teeth of the shifting sleeve come into engagement with the shifting teeth of the coupling member.