A transmission is a complex piece of machinery, and many different factors can cause it to wear down sooner than it should. Whatever the underlying cause, most transmissions start wearing out due to heat taking its toll on the individual parts. The most effective thing you can do to limit the heat on a transmission is to keep it lubricated. A common mistake is to believe that any old transmission fluid will do. Specific transmissions are built to perform optimally under particular conditions, using transmission fluid that works best for
them. So while there are more than 50 different fluids available, use only the one that is best for your transmission. You should also have the fluid changed at regular intervals to maximize transmission longevity. Your car manufacturer's maintenance schedule will tell you how often the transmission fluid should be changed. Be sure to factor in how often and how hard you drive your car. Experts define severe use on a car as driving it more than 50 percent of the time in heavy city traffic, with temperatures above 90 degrees F (32.2 degrees C). If this sounds like you, the recommended interval for changing the transmission fluid is every 15,000 miles (24,140 kilometers).
If your transmission is due for a fluid change, it's probably not a smart move to try it yourself; it's not as simple as changing the oil. An experienced service technician will inspect used fluid for contaminants and other indications of any impending mechanical problems. Regardless of who changes your transmission fluid, you should know how to check it from time to time.