Pumps, Gears, Seals, Clutches, Bands, Solenoids, Switches are some of the internal parts of transmissions. I am sure you have been told that transmissions are very complicated. Yes and No, what makes them so complicated is the amount of parts it takes to do things automaticlly and now the added electronic controlls. Understanding what each component does is not that complicated and basicly the simple part.  The key to making repairs is understanding how this components work together and knowing where to look for problems.

Inside a Ford AOD Transmission