A gear unit having a housing which has a housing part which surrounds toothed parts and oil at least partially in a housing-forming manner, wherein - the wall thickness of the housing part fluctuates periodically in one or more regions of the housing part, in particular in a straight direction, and in the region or regions the outer surface is made smooth, in particular flat, - or wherein on the inner side, in particular therefore on the surface which faces the oil and/or is the inner surface, of the housing part there are formed regions with indentations, in particular indentations which are regularly spaced apart from each other, in particular wherein the wall thickness varies synchronously with the indentations in the region or regions, characterised in that the geared motor has an electric motor and an adapter flange which is arranged between the gear unit and the electric motor [arranged adapter flange], with the adapter flange having an annular base body formed rotationally symmetrically to the axis of rotation of an input shaft of the gear unit, on which base body an axial projection is formed, with the axial projection being arranged on that side of the adapter flange which faces away from the electric motor, with the radial distance region covered by the housing part overlapping in an angle-at-circumference region not covered by the axial projection with the radial distance region covered by the axial projection, with the region covered by the housing part in the axial direction overlapping with the region covered by the axial projection in the axial direction, in particular in the angle-at-circumference region not covered by the axial projection and in the radial distance region covered by the axial projection, overlapping with the radial distance region covered by the axial projection, and with the axial projection being formed interrupted in the peripheral direction and the housing part protruding into the interrupted region. - the wall thickness of the housing part fluctuates periodically in one or more regions of the housing part, in particular in a straight direction, and in the region or regions the outer surface is made smooth, in particular flat, - or wherein on the inner side, in particular therefore on the surface which faces the oil and/or is the inner surface, of the housing part there are formed regions with indentations, in particular indentations which are regularly spaced apart from each other, in particular wherein the wall thickness varies synchronously with the indentations in the region or regions, the geared motor has an electric motor and an adapter flange which is arranged between the gear unit and the electric motor [arranged adapter flange], with the adapter flange having an annular base body formed rotationally symmetrically to the axis of rotation of an input shaft of the gear unit, on which base body an axial projection is formed, with the axial projection being arranged on that side of the adapter flange which faces away from the electric motor, with the radial distance region covered by the housing part overlapping in an angle-at-circumference region not covered by the axial projection with the radial distance region covered by the axial projection, with the region covered by the housing part in the axial direction overlapping with the region covered by the axial projection in the axial direction, in particular in the angle-at-circumference region not covered by the axial projection and in the radial distance region covered by the axial projection, overlapping with the radial distance region covered by the axial projection, and with the axial projection being formed interrupted in the peripheral direction and the housing part protruding into the interrupted region.