Vibration in 98 Contour at highway speeds

We bought a 98 Contour a few months ago, and it has recently started vibrating really bad at highway sspeeds. It start with a small shimmy at about 90-90 km/h, and gets worse until I feel my whole body vibrating bad enough to chatter my tteeth, right up to about 125 km/h where it just stops, and hums along beautifully. This is really quite irritating as I do the majority of my driving on highways. We only spent $900 to buy the car, do I really don't want to have to spend a lot to fix it

I would start with looking at the tires. Make sure they are not "cupping". If hat check out, check the balance on each tire (you will need a shop for this). If both of thse check out, you will need to look at suspension components. Wheel bearings are a slim possibility as well. It is 15 years old, and most people ignore suspension parts as routine maintenance.

I had the same initial thought, re: tires, and actually took it in to a tire shop and had them balanced on Monday. It helped marginally, but is definitely not the main problem. As far as suspension goes, do you think I would be looking more at shocks or ball joints? I've had both mentioned to me (by friends/coworkers, no one I would really take at face value as far as mechanicals go), and would really like to just have some kind of idea where to start if I do have to take it into a shop. I hate the fact they charge you $120/hr to diagnose, and come back with "well, it could be A, B, or C" so you try and pay an arm and a leg for A and B before you find out it was really the 15-minute, $50 part that constituted C :runaround: lol

Bad cv axle perhaps.

My guess is the tires are flat spotted. Wheels can still be balanced with this condition.