driveline vibration PLEASE HELP!!
 

I have a 1997 z-28 and I have this persistent vibration in the drivetrain seems like it's the driveshaft. I replaced the shaft and ujoints and had it high speed balanced. It stiil does it but only at 80mph + and it seems to do it at high rpm's when pressing the clutch between shifting at high rpm's . Any thoughts out there? There is some play at the point where the yoke and the tranny output shaft slide together, but it is minimal.

It sounds like your flywheel is out of balance. Did you recently replace the clutch or flywheel? If you had the stock one resurfaced, there is a good chance that is your problem. Another thing you could do is buy an aluminum driveshaft. They cut down on vibration quite a bit.

Either they messed up balancing the driveshaft, or its your flywheel, as Sinister sugessted.

I have not replaced the flywheel, the car has 108,000 miles on it do you think it could need balancing? The company I had do the driveshaft said it was perfectly balanced, not sure I believe them. when I first got the shaft, it started vibrating at 70+ mph. I took it back they rebalanced it, now it doesnt vibrate untill 80+. It still vibrates between shifts high rpm.

With the upgrades listed in you sig, I wouldn't doubt that you have an aftermarket clutch. If everything wasn't perfectly balanced when it was installed and a NEW flywheel was not used then you would have the issues you are describing.

Thanks all !!!! I think it is the flywheel. Will pull the tranny and kep ya informed!!