The invention includes a tool for moving a drive train component in a nacelle of a horizontal axis wind turbine, the nacelle comprising a nacelle structure (55, 56), the component being connected, in operation of the wind turbine, to a rotor (51) of the wind turbine, the tool comprising—at least one carrier (403, 405, 4041) adapted to be connected to the component, to carry the weight of the component, and to be supported by the nacelle structure, and—at least one drive unit (407) adapted to be connected to the nacelle structure and to the carrier, so as to provide a force between the nacelle structure and the carrier, so as to drive the carrier with the component in a direction parallel to the rotational axis of the rotor.