driveshaft vibration

I currently own a 93 camaro Z28 LT1 auto trans. My current problem is that at any speed over 80 it starts vibrating hellishly and at 100 mph it seems like it is going to sling the driveshaft across the highway. I don't know WTF to do, i've replaced both universal joints and turned the drive shaft 180 out from how it was aligned on the rearend with no change so i put it back in the way it was when i bought it still no difference.

any ideas?

take it out and have it rebalanced. if that doesn't work it's either bent, or not even the problem. it could be the tires out of balance.

well it's not the tires, it did it on the old tires that were on it when i bought it and the new hankooks thats on it now. How much does it cost to get a shaft balanced and if it was bent couldn't they tell me that when they balance it?

yes they will be able to tell if it's bent during balancing, at least I would sure think so. as for the cost, i haven't a clue.

thanks answers hopefully coming soon, i've had this car to 125 or 130 but i did this momentarly due to the vibration, i was looking for a driveshaft coming through the floorpan i would like to see or even know if this car can do the dash and if it isn't capable i'd like to know how far it is from getting those extra 20 or 25 MPH to bury the needle!

it'll do around 80 to 100 with great vibes but I've pushed this car to above mentioned speeds but only momentarly with great fear

really no point in going that fast, but to each his own.

A guy I work with had his WS6 vibrate bad. He thought it was the driveshaft and pulled it. A local driveline place checked the balance on it for free. Turns out the bushings were worn just enough to get the pinion angle in just the right spot.....
I have also had a bent rim ( I knew it was bent years before) and had new tires put on. The people at the tire place made no mention of it, just balanced the tires as usual.

i had a 2000 firehawk and i nhad the same problem it seems that the rims were really cruket.

does the back end seem to wander at those speeds, i noticed mine doing that today at about 90 or so on the highway. after getting it home and jacking it up i discovered the problem, bad rear wheel bearings. mine are quite severe,i have about 1/2 inch of side to side play on both sides,but i felt like i had a driveshaft vibration for quite a while. this is a pretty common problem in 4 gens. might be something to check.