Some of you were complaining of your rear differential making metallic grinding/creaking noises when going over bumps or taking curves. Same here, so I replaced the upper control arms with the FRPP ones and the upper bushings attached to the pumpkin with new stock ones. It turns out the pumpkin's upper bushings were shot! I bought a nifty tool ($38.00) from stangsuspension to remove the bushings and also installed them with the same tool. What a difference! I no longer have creaking noises emanating from the back and the back end feels much firmer. According to some suspension sites, you should use stock bushings on the uppers since stiffer aftermarket ones will bind too much and destroy your torque boxes. If your car is several years old, this is a must do.