Traction chain for an automobile vehicle including a wheel support (K) which supports a rotating hub designed to receive a drive wheel (W), and a rotating toothed wheel having the same rotation axis as that of the drive wheel, the toothed wheel meshing directly with the hub. At least two gear-wheels are permanently engaged with the toothed wheel and are rotated by an input shaft that is driven by an electric motor. A gear ratio change shifter mechanism is shiftable between first and second driving positions and a neutral non-driving position. In the first driving position the shifter mechanism directly connects the input shaft with one of the gear-wheels. In the second driving position the shifter mechanism indirectly connects the input shaft with the other gear-wheel through a transmission path which establishes a gear reduction ratio different from the gear ratio established by the direct connection.