roadking

I have a 2002 sienna which has been trouble free. It now has 50k miles not much for the year of van. My toyota pickup is my main car 310k miles and running strong. Anyway went on a long ride with van and the front end started shaking at around 65 and stopped around 75. I thought wheel balance. The more I drove the worst it became. When I got home I swapped the front pass with rear pass wheel. Took it for a test drive. The van starts shaking at 25mph. Next I swapped the drivers front/rear. same symptom. For the last year I thought I felt a rumbling in the passenger front wheel. It would come and go. I thought it was a rough road at first. Not sure but I think this might have been the start of my problem. While front wheels were off I checked for loose front end parts and all felt and looked good. Does anyone have a similar problem.