The metal particles then float around in the lubricant causing damage. Transmission fluid becomes contaminated overtime as clutch plates, gears and other internal transmission parts wear out. Transmission fluid also contains detergents that clean and remove build up on moving metal parts inside the transmission.
Transmission fluid acts as a lubricant for all of the moving parts inside your transmission and serves as a coolant and a viscous fluid that transmits power from the engine to the transmission. Many variables related to how the vehicle is driven and the environment can affect fluids, so it must be scientifically analyzed to accurately know the fluid condition. Time and mileage alone are not the best indicator of fluid depletion or the breakdown of additive packages and sludge build up.