A gear unit housing for a gear unit includes a two-sided control lever for moving two switching contacts of a circuit breaker in opposite directions. The gear unit housing includes a housing cassette having a housing base and a cover plate detachably connected to the housing cassette by screw connections and lying opposite to the housing base. A bearing shaft for mounting the control lever for rotation about the bearing shaft is connected to the housing cassette and to the cover plate and extends between the housing base and the cover plate. At least one stud element form-lockingly connects the housing cassette and the cover plate. A gear unit having the gear unit housing is also provided.