A traction mechanism (1) for an auxiliary mobility system for a wheelchair, comprising two rotating plates, separated and being able to be coupled to each other integrally in a first position, each of these rotating plates being linked to a corresponding upper limb of a user through a connecting rod, a first driving plate (2) being linked to a drive chain for transmitting movement to a wheel and a second driven plate receiving movement from the first driving plate (2). Furthermore, it includes coupling/decoupling means linking the driving plate to the connecting rod associated to said driving plate (2), and means for detecting motion linked to the activation of an electric motor and with the movement of the connecting rod, such that it is possible to obtain three different operating positions of the auxiliary system.
