First, Camaro eye candy.

I am having an issue with a vibration that shakes the whole vehicle from 77 MPH to 86 MPH and smooths out a little bit at higher speeds. I have a relatively new set of tires on the car, and rebalanced them after the vibration appeared, and it had no impact. I will rebalance them at work anyways, but I am thinking that there is another issue going on and I am having a rough time identifying it and would love some ideas.

One area of concern is the driveshaft and rear end. The driveshaft is an aluminum unit out of a 2000 Trans Am that was totaled due to a front end collision, and the rear end is out of an 88 junk car with 3.23 posi and disc brakes. I put new brakes on the rear end, but otherwise is stock.

The alignment on the car is damn near perfect, and I have had it on my Hunter rack at work several times to ensure everything is straight. I am not sure what else, aside from front wheel bearings, would cause any significant vibration at just those speeds. I replaced the front brakes a few years ago, and repacked the wheel bearings last year and they were well within tolerance.

Any ideas what could cause a vibration at those speeds? Thanks as always!

 

Have you looked at the pinion angle ?

 

Check u-joints, and it may not hurt to have the balance of the driveshaft checked.....

 

Did it vibrate before you put those wheels on?...

 

Was there one thing you changed that caused this vibration to start? If you made several changes at once, it's going to be difficult to single-out the culprit. If I were to guess, I'd go with the above-recommendation to start with the pinion/trans angle. If that's within spec, I'd look at wheel/tire balance and check wheels for out-of-true.