One of the main stages of research related to increasing the efficiency of planetary hydraulic motors operating as part of the mechatronic systems of self-propelled vehicles is the experimental research of real samples. Experimental studies of the influence of design features of the rotor system of serial and modernized hydraulic motors on the output characteristics of mechatronic systems were carried out by means of comparative bench tests. A technique has been developed for conducting comparative bench studies of planetary hydraulic motors. A test bench scheme is proposed for testing a family of unified series of high-torque, low-speed planetary-type hydraulic motors. The main factors determining the change in the output characteristics of the planetary hydraulic motor, taking into account the design features of the rotor system, are: pressure drop, flow rate of the working fluid and the error the manufacturing form of the gear profile of its rotors. Tests of planetary hydraulic motors with a serial and modernized rotor systems were carried out. The modernization of the rotor system was carried out by changing the design of the external and internal rotors in order to reduce the shape error of their gear profile. As a result of experimental studies, it was found that eliminating the error the manufacturing form of the rotors of the modernized hydraulic motor can significantly improve its output characteristics - increase the torque at specified rotation speeds, and as a result, increase the hydromechanical and overall efficiency of the mechatronic system as a whole.