First off it isn't the drive shafts.. . . . I keep them well greased and they don't have the 4Runner clunk. It sounds like a loose hub and makes the clunk in the front and rear when I hit smaller bumps. Hit a bigger bump and it doesn't happen. I have checked the hubs and they are all very tight. I am thinking it may be the XREAS shocks just because it happens on small bumps and not the bigger ones. The truck has almost 100k and they may be getting a little worn. It bugs the snot out of me because the 4R is so tight that the noise seems so out of place. Oh yeah, my spare tires is also tightly stored and the sway bar bushing are all in great shape too.