i have the 4 inch procomp. ive had 2 front drive shafts go. 1 steady bearing. and i had to replace the rear bushings on the front leafs... leafs are leafs i think. im sure it was the installers that caused the bushings by tightening them up too much and thus wrecking the rubber bushing. you may have a problem with the shafts... i personally dont know anyone else thats had this problem though. i use fwd pretty frequently so that may have something to do with it. all of this happened before 100 000 miles