Lesson 11 Manual Transmission Cars need transmissions because of the physics of the gasoline engine. First, any engine has a redline - a maximum rpm value above which the engine cannot go without exploding. Second, engines have narrow rpm ranges where horsepower and torque are at their maximum. For example, an engine might produce its maximum horsepower at 5,500 rpm. The transmission allows the gear ratio between the engine and the drive wheels to change as the car speeds up and slows down. You
