The transmission comprises a hydraulic power transmission device, a V-belt stepless shifter and a planetary gear train. At restart time when the vehicle is at rest with the V-belt stepless shifter in high gear, the hydraulic power transmission device is operated to shift for providing a relatively high torque ratio, rather than the V-belt stepless shifter. A smooth restart is thus made possible. In addition, the planetary gear train permits the shifter smoothly to switch between forward and reverse. Both features meet the transmission needs of all vehicles.