This paper describes history of CVT development and the most significant systems that allow automatic transmission gear ratio change. Furthermore, paper describes working principle of automatic transmission system and takes CVT as an example of such system. Different CVT types are specified and working principle of hydraulic CVT is described in detail with its specific parts and components. In order to provide better insight into the performance of gearbox with continuous gear shift ratio, a comparison of acceleration from 0 km/h to 100 km/h was performed, comparing a car with 105 kW motor with manual gearbox and CVT. Also, modeling calculation of CVT dimensioning was performed for a car with 75 kW which was used as a base for system modeling using Autodesk Inventor 2019 software. When designing the model, special attention was given to the construction and working principle of the hydraulic part. Based on the requirements that needs to be met in order to hydraulic circuit to function, a construction solution with a specially shaped connection between hydraulic piston and mobile pulley was performed. It was also necessary to properly design the system bearing as well as to create a specially designed housing to make the system as small as possible. Finally, work drafts of all essential system parts were made, along with circuit drawings with the BOM component, and exploded view with the BOM component.