Sorry, Bryan, I don't agree. A sports car should have a firm ride, but it should not shake or vibrate. Mine is smooth all the way to 90+, which is as fast as I have driven it.

Although I have a '78, I went thru most of what you have described. Replaced many expensive parts, bushings, mustache bar, differential etc.. End result and the final fix..........my new tires were out of round. Sounds too simple, and this might not be your problem, but please don't underestimate the effect this will have on your Z. Good luck and don't give up until you find the fix.

KMGMZ

Good point kmgmz - first thing I did was have my wheels rebalanced once the vibration started a month ago. I had installed New BFG g-Force Sports in the 2-1/2months prior and was not happy with the orginal balancing at Discount Tire? Good tires, poor balancing, had them balanced twice and I was still not happy - so I had them done by a local professional with many years of racing experience, cost me $65.00 for 5-tires inculding my spare. This made more of a difference in the front end, no steering wheel vibration or subtle bouncing.

Since all the rear end repair work above and now that I have 600miles on my new clutch, I did get my car up to 100mph Memorial Day, on the interstate - and there's no vibration. Pure engine noise and of course road bumps are about all I hear and can feel. It really seems like a different and newer car.

Many thanks..