When I first got the car it vibrated when past 80mph, and really bad when I would let off the gas and coast down from 80+mph.

So I changed the U-joints, the broken trans mount, and the leaking output shaft seal.

Now it vibrates horribly and makes a low pitched humming sound at 70mph+. at 90mph the shifter feels like a damn vibrator. The trans mount is just a stock replacement and I disconnected the driveshaft from the rear and rotated it 180*. (not sure if I needed to remove it from the trans too though) Or it could it be I bent the output shaft somehow?

 

anyone?

 

I'm wondering if the drive shaft has been modified and if so was it balanced? Just trying to think of something you may have overlooked. Hope you figure it out soon !

 

still havnt figured it out. I dont think a seal puller would generate enough force to bend the output shaft and Ive used the same brand trans mount on my previous Camaro with no problems. Im gonna look for a place that balances driveshafts

 

Steve-oh, welcome to TGO.

Odds are that the drive shaft is just plain bad. The way that GM centered the u-joints makes it near impossible to R&R them and end up with a shaft that doesn't have any run-out. The balance ends up worse then when it was stock.

Best bet is to get an aluminum drive shaft. Third or forth gen will fit.

RBob.

P.S. note that GM calls a drive shaft a "propeller shaft."