I know older Dodge caravans are famous for transmission problems, when did chrysler solve this problem?
The worst of the problems were apparently cured as of the '03 model year, but there have been posts over the past few months on newer Dodge and Chrysler vans that still appear to have problematic transmissions, so it is hard to say. Most likely anything from the '04 model year and newer will be okay, but it would probably be a good idea to do a trans fluid change (with the correct fluid!) on anything that you buy as a used vehicle.
This legend is not entirely without foundation, but has been overblown. If you are looking at a minivan - any minivan - expect its transmission to need major work at some point.