Shaking at around 85 mph

[kt1]

I've had a vibration issue that wouldn't go away, put on aftermarket wheels and vibration was still there. Lowered the car with new struts, eibach springs, and an alignment afterwards on a digital hunter machine and the vibration was still there. Had the wheels religiously balanced once every 3 months and each time the vibration was still there.

So I got fed up one day and decided to do a full inspection, all suspension components looked straight and true. All bushings didn't show signs of cracks. I was stumped until I jacked up the rear end and put it on jack stands then started the car and drove it up to 85 mph while the rear was on jackstands and the vibration was there. It ended up being my axles. So you're problem may vary, I would go with the routine maintenance stuff like alignment and wheel balancing (dynamic only!) and this is usually the source of vibration a large majority of the time.

Guess working at bridgestone has its perks because i have access to all the alignment, lifts, and balancing machines.

If it is a suspension related issue, try some simple diagnostics...
Use the 'wiggle' method to check if your tie rods and ball joints are fine. Jack up a wheel and wiggle it horizontally and vertically to see if there is any play, if there is play in the wiggle horizontally it could be a bushing or tie rod, if there is any play vertically then it could be a ball joint. Hope that helps.