Electromechanical drives with gear mechanisms (often reducers, rarely - multipliers) are used in many space, aviation and defense facilities. In the process of long-term work (more than 10 thousand hours) the gears gradually wear out, which ultimately leads to a change in the teeth profiles, their dimensions and the appearance of increased gaps in meshing. This results in a reduction in efficiency, reduced kinematic accuracy and torsional rigidity of the drive, increased dynamic loads. The intensity of wear can vary over a wide range of values, it depends on the type of conjugated surface contact interaction, materials, environmental conditions, the nature of mechanical and chemical processes occurring in the contact, the magnitude of the acting stresses, sliding speed and ambient temperature. In friction at ordinary atmospheric conditions, films of oxides and adsorbed substances are formed on the exposed wear (interacting) surfaces reducing the intensity of wear, since being broken when sliding, they block the material destruction in a thin surface layer. A technique is proposed for calculating the service life of the electromechanical drive forehead gears by the wear criteria.