The transmission system or powertrain is certain system which directs the power and momentum of the vehicle engine to its driving wheels (front, back or four wheels). In addition to provision of vehicle motor power in different directions (front or back), this mechanism causes proper momentum distribution to the driving wheels in different speeds; in other words, it provides the engine power flow and path in different vehicle motion angles. The powertrain is composed of the main assemblies including gearbox (manual and automatic), clutch assembly for manual gearboxes, propeller shaft for from engine and back driving wheels cars, differential and driveshaft. In this system the main duty of the gearbox is to change the RPM and output momentum of the engine and transmitting the same to the driving wheels in proportion to the vehicle performance conditions. Additionally, power and torque transmission ON/OFF between the engine and gearbox are conducted using clutch.