Overdrive sounds bad

Hello, can anyone help me with my 2000 4runner with automatic transmission? When it goes into overdrive it sounds and feels like a grinder. Turn the o/d button off and the noise goes away no matter what speed as long as it stays in over drive. The fluid looks and smells ok and is full. Just to give you an example of the sound, it is like the old toyota truck 4x4 standard transmission with a bad input shaft bearing. (those were the days:)

Thanks
Chris