I asked about this on the driveline board but hav'nt had any luck so far. The T/A is getting some kind of vibration at around 70 mph and it gets stronger the faster you go. The car has all new tires and all new front end, I've re-balanced the tires at two different places but still have the same problem. Has anyone had their stock driveshaft do this with 2.73's?

 

yes

 

I started noticing vibrations after changing my u-joints and getting new tires. Problem was I didn't know which one caused it since I did that about a week apart and didn't really notice till a week or so later. Any way I tried replacing the u-joints again and it didn't help. so I had the tires balanced checked and they where right on.

So I decided I must have bent the end of the driveshaft where the u-joints went in when I tried to force the stock ones out without melting the impregnated goop inside. So I bought a used steel one to give it a try. And it greatly reduced my vibration. Recently I bought new rear tires made of a softer compound for traction purposes. And my vibration has really gone down now. My previous tires where pretty hard, they had like a 420 tread rating.

So basically what I am saying is it could be a combination of things. And just because the tires are balanced doesn't neccessarilly mean they are not causing the vibration. Some tires just do that. Maybe the way they have worn is causing it.

 

If it's a slight vibration try first just flipping the driveshaft 180* on the rear pinion yoke. Sometimes works, sometimes not.

Driveshaft vibration is much higher frequency than a tire imbalance. Like just a bit lower frequency than an electric razor.

94 Formula came with the well known unbalanced stock shaft but I couldn't get it replaced under warranty becuase I wasn't the original owner. It would rattle my fillings out at 90 MPH. Flipping the shaft did not help that piece of junk- ended up buying a new Lingenfelter aluminum shaft. Totally solved the vibration.