sheave is blocked by a brake b indicated in fig3 a current preferably a constant current is then applied to the commutator motor such that the gearbox shaft 3 is axially moved to its one end stop while the gear teeth of its worm 6 are simultaneously held or roll off along the meshing opposite gear teeth of the gearbox output 7 the current direction is then reversed and gearbox shaft 3 with gearbox output 7 still blocked is axially moved to its other end stop the dips in the time current characteristic im f t shown in fig1 and fig2 which are due to the lamella junctions of the commutator are counted in an evaluation device ed shown in fig3 u2014 e g according to the method described in de 41 38 194 a1 which reference is incorporated into the present application by reference the dips are if applicable pulse amplified u2014 and are processed into a control variable representing the axial play counting can be effected with respect to the low signals or the high signals as well as by using a combination thereof fig1 shows the ripple of motor current im between a first end stop a 1 which is represented by a first lamella junction jump in the current characteristic by a low signal after a starting current pulse at the instant of the start of a rotation of gearbox shaft 3 and a second end stop a 2 which is characterized by a low signal when gearbox shaft 3 subsequently comes to a stop after having traveled through the axial play path and the end of.