My car sat for 7 years and my tranny fluid is a darkish color... I didn't change it yet... thinking about a powerflush... anyway... its an automatic and if ->I<- change gears sitting there with the shifter then it goes BUMP .. the whole car does a breif shake and its in gear.. does it for any gear I shift into.. but if i'm on the road and its changing (automatically?) there is no bumping of any sort... so whats wrong..

 

the bumping that you hear is your torque arm, that runs parallel to your driveshaft, you may want to check the torque arm bracket and make sure that the bushings aren't worn or damaged, that should fix it.