Abstract: This motorized reduction gear comprises a rotor equipped with a rotor shaft, a reduction gearbox (2) containing a gearwheel (3) in mesh with an endless screw of the shaft, a damper (5) housed in the wheel, and secured thereto so that they rotate as one; the single-piece damper has peripheral cut-outs (8) designed to accommodate, on the one hand, radial fins (7) of the wheel and, on the other hand, elements (10) for driving an output member (11), and the edges of the cut-outs are chamfered (38). The chamfers ensure that the angular deflection of the damper as a function of the torque is gradual and make it easier to fit automatically onto the hub of the gearwheel.