97 3.5 vibrates (shakes) when shifting

when i take of in my 97 3.5 the tranny will shift but as it is shifting from 1st to 2nd it vibrate (shakes) really bad them from 2nd to 3rd its not as bad. this is a three speed auto. with overdrive. im pretty sure it does not slip as it shifts thou.

first thing to do is have the trans flushed and refilled with mopar ATF+4 trans fluid this is specially formulated for these kind of issues and normally corrects the problem