I purchased some rebuilt axles the other day and installed them. After we got done we took it for a test drive to see if it solved our popping problem. It solved that, but under acceleration there is a bad vibration. The axles didn't come with the little round rubber pieces in the middle of the axle. I was just wondering if any of you guys have axles that don't have that rubber piece. We took the rebuilt ones back and got brand new ones, but they also don't have that rubber piece. Any help would be great.