A step-by-step variable transmission has a housing, a drive input shaft device, a drive output shaft and a countershaft. A plurality of gearwheel sets are mounted on the drive input shaft and on the countershaft. The gearwheel sets can be shifted so as to establish different gear stages by means of respective shift clutches. The countershaft is connected to the drive output shaft by means of a drive output constant wheel set. The drive output shaft is rotatably mounted in the region of its opposite ends on the housing by means of two bearings. At least one of the gearwheel sets is mounted in the region in the axial direction between the two bearings of the drive output shaft.