I had a problem with U bolts loosening up on me, even after short drives. Upon further inspection I noticed that the U bolts nuts were not loosening, but the shims were actually flattening out. It's doing it worse on the driver's side where the perch was caved in slightly. But the passenger side with the fixed perch is also doing it, but not as bad yet. The fellow I spoke to at superlift said he had never heard of this happening before. From my past experience with other Superlift kits, they never seem to have heard of any problems with there kits before. He confirmed that they were aluminum shims. My question is do you think I should go back to superlift and replace the shims with more aluminum ones or try to find some steel ones? I'm going to replace the perch while I got it all back apart. The lift itself probably only has 500 road miles on it and no real major wheeling miles. Superlift recommended 100 ft. lbs on the U bolts. I just crank down on them which could be the cause of the problem. Anyone every had this problem before? Thanks, Mark.