Well i when i was putting my car back together, i used a driveshaft from a '95 Z28 b/c it was painted and nice and my old one was rusty. So before i put it in i did the u joints on it. I soon found there was a very very bad vibration at 80mph..especially on deceleration. I soon switched it for an aluminum one my friend had and the vibration was gone completely...all the way up to 125mph. I then started to notice more and more as time went by that the vibration was coming back. Soon it was so bad that it would be bad at 45 mph deceleration. So i did the u joints on the aluminum ds and found that the front one was totally mangled...ok i thought..problem solved. Well now i have a vibration after letting off at 90mph..not nearly as bad as the first time with the 95 ds...but its still pretty bad. My rear tires have been balanced as well. So im out of ideas...can bad u joints throw a driveshaft out of balance? That seems to be the only option left to me..

 

i believe i have sort of the same problem i bought my car last year and it had a nasty vibration when cruising and bringing the rpms up then on deceleration it was real bad. so far i have changed the motor and rear and also the trans mount and rear suspension and new tires and rims.

since i had the vibration before i changed everything and after im leaning towards the trans or converter those are retty much the only original things left in the car besides front suspension.

 

im leaning towards the driveshaft being out of balance from drving it with bad u joints but im not sure

 

Have you check for a loose or worn pinion bearing?

 

no how would i go about doing that?

 

grap hold of the pinion yoke and try to shake it. If it has any play, up/down, side-to-side, you've got a problem...

 

o ok easy enough. I went across the whole driveline yesterday. Tried shaking the driveshaft..no play what so ever. Tightened up the tranny mount crossmemeber bolt and the tranny mount to tranny bolts...all good. Tires are all balanced as well..no missing wieghts. Ill give that pinion a shake and get back to ya, thanks.