My 96 Windstar is running perfect except for a really strange problem. At 65 and above after about 20 to 200 miles it starts a vibration that builds up to the point where I have to slow down below 30 or stop. I get out look under the hood and all is fine. I smell the tires. The driver side front tire has a mild smell of something like it might be warm. I get in and start driving, no problem. I could drive to Minneapolis and back (350 miles one way) with this happening only in the first leg of the 2 day trip. It sounds and feels like I am getting a flat, but I am not. I have had a frontend specialist look at it and he says he cannot duplicate it but has inspected it over and over and insists there is nothing unsafe. I have known this guy for 20 years and he is an expert so I trust him. He believes me, but thinks it has to progress a little more to figure it out. Please help. I only need this to drive my kids to college a few times a year. I do not want to buy another van when this is in otherwise almost perfect shape.
Check the front springs.
This year of Windstar had a recall on broken springs that would suddenly give out and blow the tire.
Perhaps one is broken and is rubbing on the indide of the tire.
I am going to guess your van has rear drum brakes. I am also going to guess that one of your rear drums has shoes that are not disengaging all the way. This could be either a sticking emergency brake cable or (what recently happened to me) the brake linings coming off the shoes and wedging against the drum. Over 65 the drum heats up enough to cause the vibration you describe. Slow down or stop and the drum cools off enough that it stops vibrating. That smell you talked about sounds like cooked brake lining. I’ll bet you a jelly donut I am right about this one.