Vehicles equipped with automatic transmissions have a lubricating fluid in the transmission that is called, appropriately, transmission fluid. Anyone even vaguely familiar with auto mechanics comprises at least that.
Unlike engine oil, transmission fluid with which it has much in common, or engine coolant , transmission fluid is usually a bright red color. This separates it from black and green coolant oil, allowing the person to car maintenance, not only to know what the liquid being treated, but easily spot leaks and to know what is your source.
The history, purpose and types of transmission fluid
Transmission fluids are first introduced in the 1950s, modified engine oils to go with the (then new) shifting automatic transmissions. Destron (owned by GM) introduced a completely unique fluid Automatic transmission fluid (ATF) in 1953 and began the fluid market specialty.
ATF lubricates and provides transmission fluid for use in the servo and cylinders. Tranny fluid is viscous at once (sticky, slippery lubricant) and able to be used under pressure. Both transmissions are qualities required for optimum performance.
So fluid main purposes are to lubricate moving parts inside the transmission fluid pressure and provide for controls within the self-shifter too.
Different fluids are purchased for different uses have different properties. The heavy-duty transport a large truck will likely have a very different fluid used in it that will do a little sightseeing. The universal additive is a dye. The traditional color of purple or red that comes from added coloring.
Lack of fluid
Unless soiled with debris (not uncommon), transmission fluid is technically feasible forever. When it becomes soiled with residues of the transmission and the moving parts, but it circulates through those transmission, causing problems. This is the reason for the greater part has tranny filters and magnets for waste disposal. These filters have regular intervals in the tens of thousands of kilometers, however.
The other thing that can ruin the trans fluid is heat. ATFs most well to about 200 degrees Fahrenheit. When used at temperatures above that, you can begin to lose its viscous properties and 300 degrees, most of them not at all. Fortunately, most vehicles are expected to operate in the 100-150 degree range.