Shifting issues
 

I have a 1996 Eldorado with 52,000 original miles on it that has some shifting issues. When it is in drive it doesn't change gears. It was sitting for a quite a few years. So; I dropped the pan and it was very clean except there was a tiny metal ball in the pan that must've come from the valve body somehow. The fluid appears to be good and clean with good color to it. Could someone explain to me the possible problem and solution.