6 months ago I purchased my XLT with 200k miles. I feel an intermittent vibration through the floorboards which appears to be coming from the right front. it feels as if my right front tire ran over a short rumble strip of say 4-5 ridges. There is no unusual noise, no change in operation. This can be at 35mph or 60 mph, or any point in between... For example - Yesterday I drove about 55 miles to a nearby town and back, average speed 55 mph with some intown driving of 25-30mph. On the way there were no vibrations. On the way back it happened 2 - 3 times, at varying speeds, several miles apart. I had the front end checked and they said everything was fine. Any Ideas? Thanks!