A drive motor (1) with a shaft (3) drives a power takeoff shaft (5) via a planetary differential gear (2). The second input shaft (4) of the gear (2) is connected to a servo motor (10) via a worm gear (6). The worm (7) of the worm gear (6) is at least half as large as the worm gear (8). The pitch angle of the thread of the worm gear (20) lies between 5.degree. and 9.degree.. The rotational speed of the servo motor is controlled by a control (9). As a result of this design, a large controllable range of rotational speed is achieved with a lower power output from the servo motor. In this way, a large output power can be precisely regulated with little regulation effort. The drive has a high dynamic ratio and is suitable, for example, for cranes and elevators.