The efficiency of tractor units (TU) is provided with the processes taking place in the machine set, considered as technical systems (TS). In order to develop theoretical understanding of the processes in the TS as the basis and purpose of repair and service impacts, presents the author's concept, based on the basic concepts of "processes in the TS", "the performers M and R", "technology M and R", "goal". Analysis of the fundamental concept of "processes in the TS" possible to identify four types of relations: order, conditioning, rigor and consistency. It is shown that the implementation of technology maintenance and repair should be carried out depending on the evaluation of the effectiveness of processes in the TS, detectable in the complex diagnosis. According to the degree of consistency of processes in the TS goals of maintenance and repair can be judged on perfection in the design of the machine part of its technical operation.

Keywords: tractor units, technical system, basic concepts, performance evaluation, technical operation