In a few of the latest cars on the market, you can shift gears simply by pressing a button, turning a knob or toggling a small joystick. Yet at the same time, plenty of different vehicles still require drivers to make use of one foot for the clutch pedal and another for the gas, all when using one hand to manipulate the gear-shift lever through a distinct pattern of positions. And several other current cars don’t possess any traditional gears at all within their transmissions.
But regardless of whether a vehicle includes a fancy automatic, an old-school manual or a modern-day Variable Speed Transmission consistently variable tranny (CVT), each unit must do the same job: help transmit the engine’s output to the traveling wheels. It’s a complicated task that we’ll make an effort to make a bit simpler today, starting with the basics about why a transmission is needed in the first place.
Let’s actually start with the typical internal combustion engine. As the fuel-air mixture ignites in the cylinders, the pistons begin moving up and down, and that movement is used to spin the car’s crankshaft. When the driver presses on the gas pedal, there’s more fuel to burn in the cylinders and the whole process moves quicker and faster.
What the transmission does is change the ratio between how fast the engine is spinning and how fast the driving wheels are moving. A lesser gear means optimum performance with the wheels moving slower than the engine, while with an increased gear, optimum performance includes the wheels moving quicker.
With a manual transmission, gear shifting is handled by the driver with a gear selector. Many of today’s cars have five or 
six forwards gears, but you’ll discover older models with from three to six forward gears offered.
A clutch can be used to transmit torque from a car’s engine to its manual tranny. The various gears in a manual tranny allow the car to visit at different speeds. Larger gears offer lots of torque but lower speeds, while smaller gears deliver less torque and allow the car travel more quickly.