So I havent gotten on the highway in a while, and I happen to see another 3rd gen tear by me. It was a blur but i noticed the RS badge so i went for him. I stomped him and then we had fun tearing up the highway.

Anyway it was bothersome, as at 85 and up its a little shaky and unplesent to drive. Ive been around it and cant figure out why its not as stable. Any ideas?

 

i think its your driveshaft. mine does the same and ive read a swap to a 4th gen aluminum driveshaft solves this problem. or you can go all out and get a stronger aftermarket driveshaft just to be really safe as far as strength goes.

 

could be driveshaft...could be worn u-joints...could be tire balance and it's not bad enough to notice at lower speeds...all of the above could do it.

 

id have to second the notion of it being the driveshaft or unbalanced tires. that is all i can think of.

 

if it is u joints unless when they first start to go youll only notice it at higher rpms because they bearings are spinning faster but if they get bad enough it can just be once you get to a certain speed. Its pretty noticeable if it is the whole car vibrates if its the u joints but most noticeably either by the front or back of the drive shaft depending on which one it is or both ends if its both.