[xeroinfinity]

Welcome to AF !

When you say your cars shakes over 80miles, was that 80 mph or after driving the car 80 miles??

Could be your CV joints causing the vibrations. My SE had a 57-62 mph shake, changed everything it still done it, untill I changed both CV joints.

if you were refering to 80mph, then it most likly the tires, because most tires are NOT rated for 80mph, except Z-rated tires which are rated for around 100mph.

Getting them balanced properly is important too. And if you hav stock wheel, alot of times those wheel weights fall of easily.
Hope that helps !