Well I did get time available yesterday so that I could put on all the parts myself. Put on the new sway bar bushings (old ones weren't all that bad, but were compressed and cracked), and put on new outer tie rods. Those were a big pain to break loose off the shaft. The tie rods were originals and totally shot - the protective boot had long ago ruptured. There was no grease inside, the ball joint inside was damaged, and the whole thing was loose and had lots of slop in it.

So anyways, got that all put on both sides (took about 4 hrs), then test drove it w/o a wheel alignment at low speeds up to 40 mph. I could tell the vibration was gone at the lower speeds at least, no clunking. Still kind of had the little bump hop, so I put on some Monroe Max Air rear shocks and that fixed that issue completely. So then this morning I had a 4 wheel alignment done to finish my suspension renovation (it was out of alignment on the computer) and headed to the interstate for high speed testing.

I used to get vibration bad starting at 60 mph. There was no shake really until I hit about 70, and it wasn't as strong as vibration as I had before my work-but it was still there. I also used to have a shake at 40 mph(that'* gone now), wheel hop (that'* gone). So as I said, it starts later now, around 70 mph, and isn't as intense. It'* kind of like a rolling shake now where it'll be bad, then die down, then come back. In high school I had a crappy hand me down 1982 Oldsmobile Ciera and it had the exact same problem. Glad to see GM got its act together in that 18 year time span.

Basically, the shake I do feel is in the accelerator pedal, a little bit in the steering wheel, and a little bit in the seats. The dash doesn't shake much at all anymore.

So overall, the parts cost me about $150: $70 for the rear shocks, $15 for sway bar bushings, and $65 for both outer tie rods. I put them in myself, alignment was $50, so spent about $200 plus my time and things are quite a bit better - especially in my town driving, which I do about 95% of the time. Rides like glass, no shakes shimmies or noises now.

As for the 70 mph vibration, I imagine I'll have to accept the vibration it in its reduced state. I'll see if I can track down anything about the accelerator pedal and/or steering wheel vibrations, but those are steering rack etc. issues that probably won't be solved. I'll continue to tinker maybe in the future with a Hunter balancing to see if that'll take a bit more out, but this remaining core vibration in the steering system seems structurally imbedded. I also think my motor mounts aren't the greatest either, because the engine does vibrate some at idle, and my vibration at 70 mph does get worse when I accelerate from 70 mph, then dies down when the foot comes off the gas.

Part of the issue for me is that it'* a beautiful car, comfortable seats, has some charm and character, and rides well in town, but it'* all somewhat diminished by the fact that it can't handle the true test of handling like a real car when you have to push it at speeds and it vibrates.

But for me at least, most days I don't worry about it cause I'm cruising around surface streets, so I only curse the GM gods when I'm doing long trips.

great update!

I agree all on counts, though I personally feel that when "pushed" my supercharged edition does respond like a real car. Don't forget these a very big cars. And I must say that the Corvette like anti sway/anti-roll suspension has save me and my ride more than once from perilous situations.

Well I'm off to find some bushings and will report back on any improvements.