The top drive comprises a gear unit, a main spindle, and an active pressure generating device. The gear unit comprises a gear housing, an axial main bearing, and an axial auxiliary bearing. The axial main bearing comprises an upper main bearing part with rotates relative to the lower main bearing part. The lower main bearing part contacts the gear housing. The axial auxiliary bearing comprises an upper auxiliary bearing part which rotates relative to the lower auxiliary bearing part and contacts the gear housing. The main spindle rotates within the gear unit and contacts the upper main bearing part. The active pressure generating device is arranged between the upper auxiliary bearing part and the gear housing, the lower auxiliary bearing part and the main spindle, the lower main bearing part and the gear housing, and/or the upper main bearing part and the main spindle.