A gear transmission mechanism (2) for motor vehicles having a main shaft (10, 12) and a countershaft (14) parallel to one another, on which different gears for different gear ratios are arranged. The countershaft (14) is arranged above a horizontal plane (X-Y axis) containing a main shaft axis (16) with respect to the axle system of the vehicle so that installation space for the functional components (gearshift elements 18, a hydraulic system 20) of the transmission is available below the gearset formed by the gearbox wheels.