How Automatic Transmission Works

If you own a car with automatic gearbox, you’re probably curious to know how automatic transmission works. Turns out the modern automatic transmission is the most complicated mechanical component in an automobile. It contains mechanical systems, hydraulic systems, electrical systems and computer control, all combining their forces to make a car run smoothly. This article means to explain how automatic transmission works and what you can do to keep it in good condition or notice in reasonable time if something is wrong with it.


The main differences between a car with automatic transmission and one with manual transmission are that the first has no clutch pedal and no gear shift. Once you put the transmission into drive, everything goes automatic. Though both transmissions achieve the same thing, they do it through different methods; they allow the engine to operate smoothly in its narrow range of speeds, while providing a wide range of output speeds. If it weren’t for transmissions, cars would be limited to one gear ratio which would have to be selected to permit the car to drive at a desired top speed. Therefore, the transmission uses gears to make better use of the engine’s torque and to keep it running at an optimal speed. Another difference between how automatic transmission works and how manual transmission works is that the latter locks and unlocks different sets of gears to the output shaft to attain various gear ratios, whereas with the first the same set of gears can produce all the different gear ratios needed.

In order to better understand how automatic transmission works, we must take a look at the ingenious parts that form it. First, we have the planetary gearset, which is the one responsible for creating all the different gear ratios that the transmission can produce. Other parts, like the set of bands that lock parts of a gearset, the set of three wet-plate clutches, the hydraulic system and the gear pump that moves transmission fluid around, only serve to help the planetary gearset work as it’s supposed to. The planetary gearset has three main components: a sun gear, the planet gears and their carrier and a ring gear. All these components can be input, output or held stationary.

The technology and science that make the automatic transmission work is all very complicated and complex and only someone used to car components and physics could entirely understand all the work that went in there. Still, that doesn’t mean that the common driver can’t know a bit about it, at least enough to realize when something is wrong and needs repair. First of all, one should watch for leaks and stains under the car, as that may come from the transmission and could affect the power steering system. Secondly, the transmission fluid should be checked regularly for color and odor and the driver should pay attention to new noises, vibration and shift behavior.