The tool includes a first support element with: a first resting surface for allowing the tool to rest on the floor; a first support surface and a second support surface for respectively supporting on the same a first arm and a second arm of a first support of the subset that supports a low-speed shaft. Between the first support surface and the first resting surface is a first distance that is different from a second distance between the second support surface and the first resting surface. The difference in distances allows the low-speed shaft to be transported in a container according to an inclined orientation, with the maximum dimension thereof oriented according to the diagonal of the container, thereby simplifying the transport costs and logistics.