Cars and

As you can see, there are a lot of moving parts inside an automatic transmission. It uses a combination of mechanical, fluid, and electrical engineering to give you a smooth ride from dead stop to highway cruising speed. So let’s walk through a big picture overview of the power flow in an automatic transmission. The engine sends power to the  torque convertor’s pump . The pump sends power to the torque converter’s  turbine  via transmission fluid. The turbine sends the transmission fluid back to the pump via the  stator . The stator multiples the power of the transmission fluid, allowing the pump to send more power back to the turbine. A vortex power rotation is created inside the torque converter. The turbine is connected to a central shaft that connects to the transmission. As the turbine spins, the shaft spins, sending power to the first  planetary gear set  of the transmission. Depending on which  multiple disc clutch  or  ...

As your vehicle reaches higher speeds, it needs less torque to keep the car going. Transmissions can increase or decrease the amount of torque sent to the car’s wheels thanks to gear ratios. The lower a gear ratio is, the more torque is delivered. The higher a gear ratio is, the less torque is delivered. On a manual transmission, you have to move your gear shift to change the gear ratios. On an automatic transmission, gear ratios increase and decrease automatically. And this is able to happen thanks to the ingenious design of a planetary gear. A planetary gear consists of three components: A sun gear.  Sits at the center of the planetary gear set. The planet gears/pinions and their carrier.  Three or four smaller gears that surround the sun gear and are in constant mesh with the sun gear. The planet gears (or pinions) are mounted and supported by the carrier. Each one of the planet gears spins on their own separate shafts that are connected to the carrier. Planet g...

Purpose of a Transmission Before we get into the ins and outs of how an automatic transmission works, let’s do a quick review of why vehicles need a transmission  of any kind  in the first place. As discussed in our primer on how a car engine works, the engine of your vehicle creates rotational power. To move the car, we need to transfer that rotational power to the wheels. That’s what the car’s drive train which the transmission is a part of  does. But here’s the problem: an engine can only spin within a certain speed in order to operate efficiently. If it spins too low, you wouldn’t be able to get the car moving from a standstill; if it spins too fast, the engine can self-destruct. What we need is some way to multiply the power produced by the engine when it’s needed (starting from a standstill, going up a hill, etc.), but also decrease the amount of power sent from the engine when it isn’t needed (going downhill, going really fast, slamming on the brakes). ...