Types

• There are two types of transmissions. The technical terms would be unsynchronized and synchronized. You may know them as manual and automatic.
  
  

Functions

• In the unsynchronized or manual transmission, you have to engage in using the clutch to shift gears manually. You will find this type of transmission in trucks or racing cars.
  The synchronized or automatic transmission automatically changes gears for you at certain speeds. Automatic transmissions are found in many different types of vehicles.
  
  

How do they work?

• The unsynchronized transmission responds when you use the clutch. Once you push down on the clutch and position your shift to the desired gear, a signal is sent to the transmission to either speed up or slow down.
  A synchronized transmission differs in that no action is required by you, the driver. The transmission is set up to respond to the speed of your car. If you are going a certain speed, then your transmission sends a signal to your engine to change to the corresponding gear.