The transmission is a very important part of any vehicle because that is what makes the vehicle go. There are many gears in it, such as drive, reverse, neutral and overdrive. There are many people that take very good care of their transmission while others do not.
When a transmission is taken good care of, it will last for a very long time. If it is not kept full of transmission fluid or is abused, it is not going to last a long time. Some transmissions can be rebuilt instead of being replaced when something goes wrong. Other times, the transmission would need to be replaced with a different one. More info: Transmission Silver spring