Abstract: To improve the traction and dynamic characteristics of small class cars, this study proposes the modernization of the power unit. The power unit includes a powerplant, clutch and gearbox. This study proposes a modernized driven pulley to increase the range of transmission ratios. The calculation of the gearbox to include the rear gear, the kinematic calculation of the V-belt transmission. Modernization of V-belt transmission was to create a two-section driven pulley with automatic locking of the outer section relative to the inner, increasing the diameter of the driven pulley compared to analogues.