The job of a car's transmission is to make sure that the right amount of power goes to your wheels to drive at a given speed. It works by shifting gears in a very similar fashion to what you see on a multi-speed bicycle.
It’s important to have enough transmission fluid. If it runs low, the transmission will run hotter and won’t have the protection it needs to cope with the added stress of towing. Transmission fluid breaks down and gets dirty over time. Whether you have an automatic or manual transmission, you need to have it serviced on schedule to make sure it runs efficiently.
An automatic transmission contains a maze of passages through which the fluid has to pass to keep it shifting smoothly. If you neglect transmission service, the passages can get clogged up and you start to have problems.
Neglect your transmission for too long, and it can fail. You really don’t want to pay for a major transmission repair.