Purpose. Theoretical and computer research and determination of performance efficiency of three and fourstage gear dif ferentials in speed changing devices through sun gears. Substantiation of the possibility of their use in machine drives based on estimating their energy efficiency and possible selfbraking. methodology. To solve this problem, we used the method of "potential power"; by computer simulation, analytical expressions for the performance efficiency are obtained; using the MS Excel software package, the graphical dependencies of energy efficiency on the gear ratio, the angular velocity of the sun gear and the number of stages are obtained. findings. The obtained graphic dependences for the performance efficiency of three and fourstage gears differentials allow one to follow visually the change in the value of the efficiency, depending on the angular velocity of the sun gear, the gear ratio and the number of steps. This allows us to estimate the perfection of the given differentials in terms of energy consumption and possible selfbraking. originality. For the first time, analytical expressions were obtained for a more precise determination of the efficiency of a three and fourstage differential gears with a driving carrier and a driven ring gear, or vice versa. Obtained from the analytical formulas, graphic dependences for the performance efficiency allow one to follow the change in the value of the performance efficiency. Practical value. It is recommended for implementation in designing and constructing practice when developing the speed change devices through the differential transmissions of drives of various machines. It can be used in the educational process of technical higher educational establishments in mechanical engineering disciplines in the study of machines drives.