A snow-trail grooming vehicle has a driving chain or track system and a cable assist pulling system having a cable winch. A method for controlling the cable winch includes the steps of detecting the speed of the driving chain, detecting the speed of the cable, comparing the detected speed of the driving chain and the detected speed of the cable, and determining a desired value for the speed of the cable, then controlling the cable winch to attain the desired value for the speed of the cable.