The graph analytical method of comparative evaluation of the transport and technological machines aggregates feasibility, which can be used in the development and improvement of the design of machines and equipment, is presented and tested on the example of gearboxes of various designs. Market conditions of management require the construction of machinery and equipment corresponding to a high level of operational adaptability as well as the ability of specialists to compare and evaluate a design at the planning and production engineering stages. The article is devoted to the substantiation of assessment tools and evaluation methods and to the development of recommendations for improving the operational manufacturability and maintainability of various designs of machines units in order to reduce operating costs for their maintenance and repair. The authors have established that the design of a constant-mesh transmission is more advanced. The reduction in the replacement time of individual parts, in particular the secondary shaft of the gearbox is 16% compared to the replacement of the same shaft of the gearbox with mobile units. Due to the improvement of the technological process of disassembly and assembly by using a special mandrel, the duration, and hence the complexity of replacing the secondary shaft of the gearbox of the TLT-100 tractor is reduced by 27%.