Rear traction ground vehicle comprising • an internal combustion engine arranged longitudinally with respect to the vehicle and a respective gearbox having an output shaft, • a rear axle, • a two-shaft torque distributor having - a first and a second transmission shaft parallel to each other, - rotating connection means comprising at least a fixed gear ratio (23/33, 24/34), - an external case containing at least said transmission shafts (2, 3) and the rotating connection means, wherein each transmission shaft (2, 3) comprises two opposite ends ((21, 22),(31,32)) that can be reached from the outside of the case, each one of said ends (((21, 22),(31,32)) comprises connection means (21.A, 22.A, 31.A, 32.A) to an external transmission shaft and a first end of said first shaft is operatively connected with said output shaft of the gearbox, a second end of said first shaft is operatively connected with said rear axle and an auxiliary motor is operatively connected with one (31, 32) of the ends of said second shaft, wherein said rotating connection means comprise at least a first gearwheel (33 or 34) coaxial with and fixed to one of said two transmission shafts (2,3) and an operatively corresponding second gearwheel (23 o 24) coaxial and rotatably associated to the other transmission shaft (3, 2), the gearwheels lying on the same plane and engaging reciprocally between each other in operating conditions and wherein the distributor comprises selection means to select said second gearwheel (23 or 24) making it fixed with respect to the other transmission shaft (3 or 2), characterized in that said rotating connection means comprise at least a third gearwheel (33 o 34) coaxial with and fixed to one of said two transmission shafts (2,3) and an operatively corresponding fourth gearwheel (23 o 24) coaxial and rotatably associated to the other transmission shaft (3, 2), the third and the fourth gearwheel lying on the same plane and engaging reciprocally between each other in operating conditions defining a second different gear ratio defined by said first and second gearwheel (23,33 or 24,34) and wherein said selection means are suitable to select one or none of said second and fourth gearwheel (23 o 24) realizing said first or said second gear ratio or neutral and in that at least one of said first and/or second ends of said first and/or second shaft comprises a clutch (25, 35, 26, 36) in order to allow one of said connection means (21.A, 22.A, 31.A, 32.A) to be disconnected from its respective transmission shaft (2A, 3A) and in that said selection means and/or said clutch (25, 35, 26, 36) is a dog-clutch. • an internal combustion engine arranged longitudinally with respect to the vehicle and a respective gearbox having an output shaft, • a rear axle, • a two-shaft torque distributor having - a first and a second transmission shaft parallel to each other, - rotating connection means comprising at least a fixed gear ratio (23/33, 24/34), - an external case containing at least said transmission shafts (2, 3) and the rotating connection means, - a first and a second transmission shaft parallel to each other, - rotating connection means comprising at least a fixed gear ratio (23/33, 24/34), - an external case containing at least said transmission shafts (2, 3) and the rotating connection means,