Our 06 Grand Caravan has developed this weird issue. When turning the wheel it'll vibrate the whole van the floor the van seat and steering wheel. Only does it when sitting or going slow in a parking lot. I did change the power steering fluid and the reservoir since I read about a possible clogged screen causing this issue. Neither thing helped. The power steering pump isn't making any odd noises. The van had 126,000 miles on it.