[HummerJim]

Yes, there are threads on this. One has you silicone lubing and adjusting the body mounts and another by HumTech has a fix where you take out the battery and give it a few pops in that area with a rubber mallet. One other was told by the dealer that it's a common problem of oil canning with the floorboards and comes and goes as temperatures change. SUVs seem to do this much more than SUTs. Take your pick!