The present invention relates to a downhole driving unit (11) for insertion into a well, comprising a driving unit housing (51), a hydraulic motor (23) comprising a hydraulic motor housing (93), a wheel assembly (90) comprising a stationary part (91) and a rotational part (92), the stationary part being connected with the driving unit housing and being rotatably connected with a rotational part, the wheel assembly comprising a wheel ring (99) for contacting an inner wall in the well and connected with or forming part of the rotations part. The wheel assembly further comprises the hydraulic motor (23) so that the stationary part and the rotational part constitute the hydraulic motor housing, the hydraulic motor comprising a rotatable section (84) connected with the rotational part for rotating part of the wheel assembly. Furthermore, the wheel assembly comprises a planetary gearing system (95) comprised in the hydraulic motor housing and the hydraulic motor comprises a rotatable section driving the wheel ring through the planetary gearing system. The invention furthermore relates to a downhole system comprising the driving unit and to use of such driving unit.