It sounds like you have a bad inner C/V joint. You have 2 driveshafts in front with a "constant velocity" joint on each end or each shaft. A bad inner joint will act like that and I've seen many of them on chrysler mini vans. It may be difficult to determine which side without removing them both so you may have to just have both of them replaced. Also have it checked for broken motor mounts as that will make the problem worse.