A gearbox for a planetary gear having a hollow-cylindrical housing body having a first internal gear, and a bearing flange engaging at least in sections coaxially in the housing body, so that an overlap area is formed, wherein the housing body and the bearing flange are firmly bonded to each other in the overlap area by laser irradiation welding. The bearing flange has a second internal gear in the overlap area. The gearbox relates to a planetary gear and a motor/transmission combination having such a gearbox and a production method thereof.