Hey guys,

I've been living with an incredibly irritating vibration at speeds between 40-80+mph. It seems to be ever-present, but worse, or more noticeable at some times than others (no particular rhyme or reason to when or why it's worse or better). Doesn't appear to be any better or worse on accel, decel or coasting. I've pretty much ruled out it being a wheel/tire issue as I've tried two different sets of wheels, two different sets of tires, road-force balanced the first set of wheels to the first set of tires, installed four brand new tires and road force balanced them, checked the wheels for bends/runout etc. No wheel/hub corrosion.

I'm thinking it must be either brakes or driveline vibration. All of my brakes were done this year; the rear rotors are new, new pads, and freshly lubed rear slide pins; rear calipers rebuilt two years ago. Front rotors resurfaced this year with new pads and new caliper pins and hardware. All the pistons seemed to compress fine. Doesn't mean they're perfect, of course, but the vibration was there before and after the brake work.

Front suspension is all new, for what it's worth. New struts all around.

Engine/trans/diff mounts are original. Driveshaft bearings/cv joints original. RF axle was replaced with an inexpensive new one about two years ago (currently my #1 suspect, followed by the driveshaft). I do hear a low faint humming from what I'm thinking is the driveshaft or rear diff but it's always been there since I bought the car almost four years and 35k miles ago. Car has 103k on it now.

How would I check for a braking/driveline related vibration? I tried driving it in the air with the traction control turned off but the car didn't much seem to like that. I'm pretty much trying to avoid having to take it to the dealer and paying them to find out for me... Any ideas would be greatly appreciated; thanks!