This happens on some S550 mustangs when launched hard. BMR and Steeda offer upgraded bolts for mustangs to try and help solve the problem. Some people (such as myself) drilled out the threads in the bushings and diff and through bolted them. This holds it much more solid and allows you to use a bolt that place the load on the shank of the bolt instead of on the threads. After seeing this I might consider doing it on my RS.