Please Help this vibration is driving me crazy!!
 

I have an 86 turbo coupe which I converted to 5.0ho 5spd. I ran the stock rear until it took a dump at week ago. I picked up a 8.8 3:55 rear that my buddy ran in his mustang. So I installed the rear and I have had a wicked vibration ever since. I tried everything I could think of, rotating the driveshaft, transmission mount, rebalanced the driveshaft??? I now have no clue, the rear ran fine in my friends car, no why the vibration??please help

Is the vibration at a certain speed or RPM??, If it is at a certain speed i would think maybe the drive shaft. I put new gears in my rear and had a terrible vibration at about 55 to 65 MPH, it felt like the whole car was going to fall apart. I had the stock drive shaft rebalanced and everthing and that helped a little but still it was there, so i finally took everyones advice and bought the FMS Aluminum drive shaft and it worked like a champ, just something was up with the stock one...go figure....good luck tho hope you figure it out!!!

i have the same problem, soon as i put that 3.55 in the pig started shak'n like no tom.