Rep Power: 0

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.

 
Rep Power: 815

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.

 
Rep Power: 783

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

 
Rep Power: 0

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.

 
Rep Power: 815

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.

 
Rep Power: 0

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