In many complex mechanical systems, transmissions of power and moving could be also found, besides the mechanical transmissions of holonomic character and the mechanical transmissions of power with nonholonomic connections. This type of transmission is characterized by having the connection of differential character between transmissions elements. Nonholonomic mechanical transmissions can be recognized as speed variators contained in many complex systems of modern techniques and the new automotive enginnerings too. Besides the variators with stiff and elastic elements there is a new kind of variator, type of harmonic drive. The aim of this paper is to describe dynamically the behavior of one of the general examples of power and moving transmissions of nonholonomic character in automotive engineerings and to estimate the stability of working system with changeable working regime. For dynamical description of moving we get the answer concerning the working stability as well as the dynamical and kinematics behavior of observed system. The obtained results will serve as one of the constraints in choosing optimal parameters in the synthesis of power transmissions in the field of vehicle systems.