A method for controlling a traction system of a vehicle, said system comprising: - a first traction wheel forming part of a first propulsion system, - a second traction wheel forming part of a second propulsion system, - at least one sensor (10a, 10b, 10c) indicating vehicle speed and/or wheel speed for at least one wheel (2a, 2b, 7a, 7b, 11a, 11b), - a control unit for controlling said first and second propulsion system (12, 13), wherein said method comprises the steps of; - manually or automatically detecting if the vehicle is stuck on the ground, - manually or automatically start up an automatic rocking free mode wherein the first and second propulsion system (12, 13) are independently controlled by the control unit to cooperate and provide traction force which alternates between backward and forward traction, said shift of direction of traction will be made in dependence of the sensed vehicle and/or wheel speed; - manually or automatically end the rocking free mode when it is decided that the vehicle no longer is stuck to the ground, and wherein the method further comprising; - the first propulsion system is controlled to mainly provide traction force in a first direction, i.e. forward or reverse, while the second propulsion system is controlled to mainly provide traction in a second direction opposite to the first direction, or;. - when it is decided to perform a change of traction direction from a first direction to a second opposite direction is one propulsion system (12 or 13) controlled to change its traction to neutral first and the other propulsion system (13 or 12) is controlled to continue to propel in the first direction for a longer time than the one propulsion system (12 or 13) and the one propulsion system (12 or 13) will start to provide traction in the second, opposite direction at the same instant the other propulsion system (13 or 12) will stop to provide traction in the first direction. - a first traction wheel forming part of a first propulsion system, - a second traction wheel forming part of a second propulsion system, - at least one sensor (10a, 10b, 10c) indicating vehicle speed and/or wheel speed for at least one wheel (2a, 2b, 7a, 7b, 11a, 11b), - a control unit for controlling said first and second propulsion system (12, 13), - manually or automatically detecting if the vehicle is stuck on the ground, - manually or automatically start up an automatic rocking free mode wherein the first and second propulsion system (12, 13) are independently controlled by the control unit to cooperate and provide traction force which alternates between backward and forward traction, said shift of direction of traction will be made in dependence of the sensed vehicle and/or wheel speed; - manually or automatically end the rocking free mode when it is decided that the vehicle no longer is stuck to the ground, - the first propulsion system is controlled to mainly provide traction force in a first direction, i.e. forward or reverse, while the second propulsion system is controlled to mainly provide traction in a second direction opposite to the first direction, or;. - when it is decided to perform a change of traction direction from a first direction to a second opposite direction is one propulsion system (12 or 13) controlled to change its traction to neutral first and the other propulsion system (13 or 12) is controlled to continue to propel in the first direction for a longer time than the one propulsion system (12 or 13) and the one propulsion system (12 or 13) will start to provide traction in the second, opposite direction at the same instant the other propulsion system (13 or 12) will stop to provide traction in the first direction.