A bit of a unique situation here. When I got my car it had a vibration at highway speeds which I chalked up to the old tires that are on it (good tires but more then likely around 10 years old).

So I took the car on a 1000km road trip this past weekend and swapped out my steel drive-shaft with an aluminum drive-shaft. I have never driven the car it came off of but it looked to be in good shape. The rear u joint had some rust on the end caps but nothing too bad. One of the end caps actually came off and a bunch of the pins fell out. I put them all back in and installed it.

Now at around 65mph I get a vibration that I can feel under my seat. It drives smoothly to that point and around town there is no vibration at all. I can even feel it in my steering wheel a bit, as well as pedals.

I have now found that my passenger side wheel does not spin as freely as the drivers side in the front. Which I have chalked up to a sticking caliper or wheel bearing, I am leaning to the caliper because I get a slight steering wander when I hit the brakes. On the highway the car almost feels like its being slowed down when you let off the gas and almost like your fighting the brakes to go over 70mph.

I am having a hard time figuring out if the road trip I took it on threw off the old tires even more or the drive-shaft is the issue or the sticking wheel up front. Possible U joint? The shifter does not really shake at all if that means anything. The car is lowered 2" and the monroe rear shocks have started to leak because of it, if that has anything to do with these symptoms

 

Ya i would start with the tires, sounds like a rolled/broken belt in the tires. And it will only get worse take them to a shop and have them checked.