A propulsion system includes two electric motors, a gearbox with at least three forward gears and a control unit to control the electric motors and the engagement of the gears. The gearbox includes two primary shafts, one associated to with the odd gears and the other with the even gears and are permanently connected each to a respective electric motor. The control unit controls the two electric motors and the engagement of the gears of the gearbox to provide at least a first operating mode in which the first gear and the second gear are engaged at the same time and a second operating mode in which the second gear and the third gear are engaged at the same time. In each of these operating modes the torque being transmitted by both the electric motors.