If there is no play in the steering its the sway bar rubber mount as these guys say below: dodgetalk.com/forums/showthread.php?t=73109 I had the same problem and it was the struts up front. The retaining nut had a little bit of play between it and the top plate. I just took the strut out tightened it down and reinstalled.
Its about a 1.5 hour job for the moderately experienced.
I have a 2002 Dodge Grand Caravan ES, with 110, 200 miles. I am a Registered Nurse by trade, and a journey man when it comes to fixing my cars. The problem I was experiencing was a rattling noise every time I went over rough roads, speed bumps, pot holes, and cobblestone entrances.
I noted that both the left and right sway bars had broken swivel on the bottom. Therefore I replaced both sway bar links.