A method for controlling a power assisted propulsion system in a motor vehicle so as to perform a transition from a lower gear to a higher gear without interrupting a driving torque applied to driving wheels; the propulsion system displays an internal combustion engine provided with a drive shaft and a power assisted transmission including: a power assisted mechanical gearbox provided with a primary shaft connectable to the drive shaft and a secondary shaft coupled to a transmission shaft which transmits motion to the driving wheels; a power assisted clutch interposed between the drive shaft and the primary shaft of the gearbox to couple and decouple the drive shaft to the primary shaft of the gearbox; a power assisted brake; and an epicycloidal gear having three rotating elements: a first rotating element coupled to the drive shaft, a second rotating element coupled to the secondary shaft of the gearbox, and a third rotating element coupled to the brake.