Anyone who has ever driven both a manual transmission car and an automatic transmission car can tell you there is quite a bit of difference between the two types of transmissions. There is a manual clutch inside the car with a manual transmission while there is no manual clutch for the one with an automatic transmission. Also, there is a gear shift within the car with a manual transmission when there is no true gear shift in a car with an automatic transmission. Instead, the “gear shift” only needs to be placed in “drive” in order for the car to move forward. No other shifting is required in an automatic transmission car during regular driving.
Automatic transmissions are amazingly complex when compared to manual transmissions. First, there are a variety of gears you have to select from in a car with a manual transmission, and all are separate gears within the transmission housing. Inside a car with an automatic transmission, there is only one gear, and it’s often called the planetary gearset. This part of the automatic transmission is able to shift between all of the different torque and speed settings your car requires during driving. Also found here is a set of bands that lock parts of the gearset as well as three or more wet plate clutches to lock other parts of the gearset. Along with this is a large pump that moves transmission fluid throughout the transmission to allow proper lubrication and cooling.
There are three main components to the planetary gearset, including the sun gear, the planet gears (along with the planet gears’ carrier), and the ring gear. Together, these form a pattern that is reminiscent of the solar system, hence the name for the gearset. Each part plays its role, allowing for one planet gear to engage another, depending on the particular gear range called for by your operation of the car. Quick adjustments can be made by an onboard computer which calculates engine speed and torque.
The “greater” and “lesser” sun gears (sometimes called smaller or larger sun gears), will also engage planet gears. The sun gears are more directly moved by a large flywheel that provides the linkage between the engine and the transmission, allowing for a complete conversion of power and torque required at the moment by the car. If it were not for this assortment of gears within the planetary gearset, the engine would overheat while trying to provide sufficient speeds for highway driving.