A gearbox comprises a row of parallely mounted disks. The mutually facing diametral planes of the disks are carrying cylindrical rings mounted coaxially to the rotation axes of the disks and provided with engaging elements on their internal and external cylindrical surfaces. Due to an offset between the neighboring disks providing for eccentricity between their parallel rotation axes all the rings located in the space between the diametral planes of the neighboring disks are in permanent engagement. Each ring is freely rotatable and is provided with means for its controlled interlocking with the disk carrying it.