Moving Within The Planets: An Explanation Of Planetary Gearsets In Transmissions

When you think of driving a car, you probably give no thought to planets, how planets move, or even how cars move for that matter. You just plug in the key, turn the car on, shift your automatic transmission into gear, and go. Yet, the movement of the planets is closely related to the movement of your car. How? The answer has everything to do with planetary gearshifts in your car's transmission.

What Planetary Gearshifts Are

If you have ever played with moving gear toys as a kid, you may already understand something about gearshifts. They are several gears acting on each other to move the entire set in a particular direction. With planetary gears, you have gears within gears. The outer ring gear is like a ring on Saturn; everything inside it, including the planet, moves around inside the outer ring.

Then there are the "planets" themselves. In each gearshift, there are four "planet" gears, which are round and revolve around inside the ring while avoiding each other. The "planets" also revolve around a center gear, which, coincidentally, is called the "sun gear." A "carrier" holds the planets and the sun in position inside the ring, much like gravity holds the planets in place in the universe.

What Planetary Gearshifts Do

Planetary gearshifts each control one shift motion within the transmission. Most automatic transmissions have two full sets of planetary gearshifts with two suns, thus giving the vehicle eight shift positions. Because the transmission is an automatic, all you have to do is pull the shift handle into one of the eight positions, and the planetary gearshifts take over and move into their proper positions to make the "universe" work together.

When Something Is Wrong with the Planetary Gearshifts

When something goes wrong with your planetary gearshifts, it is often because there is a leak in transmission fluid or there is so much rust and corrosion that the gears cannot work as they should. Transmission repair is inevitable. If you do not repair this problem when you start noticing issues with shifting into this or that gear, you could end up with a transmission that breaks and falls right out of the bottom of your car.

Because the "planets," "rings," and "suns" are deep inside their own protective "universe," your mechanic has to take the transmission out completely. Then he or she has to completely disassemble it to find the damaged parts before replacing them. This is the biggest reason why time, money and labor all come with a high cost where transmissions are concerned. Your mechanic is essentially "God" repairing your auto "universe." For more information about how planetary gearshifts work, contact an auto shop such as Karry's Automotive Service Center.