Well, i had one of these on my car and with my new combo including 4.30s and poly mounts in the rear end this thing vibrated like crazy. So i took it into a driveline shop and sure enough it was way off. Aparently both of the ends were off center and had some huge weights to try and correct the problem (which failed to do so). Anyway, be forwarned if you buy one of these recycled pop cans that they may or may not come balanced properly.