A drive mechanism comprises a transmission as well as an electromotor/generator. The transmission is connected via an input to the electromotor/generator and via an output to the wheels. The transmission has two planetary gear sets having three rotational members each, of which first rotational members are connected to the input, second rotational members are connected to the output and third rotational members are connected to a first and second brake respectively. By actuating either of the brakes a speed transforming gear is created between the input and the output. By actuating one brake during the releasing of the other brake, it is possible to switch between the two speed transforming gears without an interruption of the torque transfer from the electromotor/generator to the load or vice versa.