Most people never really tend to question how various parts of their car work, as long as they keep working as intended. While there’s nothing wrong with that, it’s always great to wonder about these things. A car’s transmission is one of the more complex parts of a vehicle, especially if it’s automatic. The main reason for this is due to its use of planetary gears.

But if they’re so complex, why do we use them? There are a few reasons why automatic transmissions use planetary gears, but before we cover that, let’s go over what they are and how they work.

What Are They?

So, let’s start out with what a planetary gear is. It’s actually a combination of multiple gear sets. The sun gear sits in the middle with three planted ones spread around it. Those planet gears then become enclosed by a ring gear, which is what makes the system fully connected. Finally, each planet gear is attached to a carrier, the primary output. Some transmissions have three separate planetary systems inside of them to control the vehicle. However, others use a system that doubles up the sun and planet gears in order to condense the system while still having access to five gear outputs.

How Do They Work?

Due to the nature of these systems, there are quite a few sequences of turning that the gear can go through to power the car. The weaker ones are used for lower gears, while the more powerful ones kick in when the vehicle reaches higher gears. The use of multiple planetary gears allows for wider variation inside the transmission. If any of these parts were to ever malfunction, this vital part of the car would be practically unusable. That’s why you’ll want to talk to an automatic transmission part supplier, like us, to buy replacement parts in the case that one of the gears in your system breaks.

Why Do Automatics Use Them?

Now it’s time to cover why automatic transmissions use planetary gears while manuals don’t. To start, manual transmissions utilize the clutch to change gears, which is a much simpler design. However, one reason why automatics opt for the planetary approach instead of a clutch-based version is that the planetary gears allow for a much smoother transition when shifting. Automatics can use a clutch system, known as dual-clutch transmissions, but they are quite clunky when they change gears, leading to an undesirable experience.

Another reason is that planetary gears are more compact. Since automatic transmissions have more parts than manual ones, they need to make better use of the space they’re provided, and the planetary gears help tremendously with that.