I think, eventually, we will all get to the clunk. From what I understand, it is in then nature of the design. The only way to avoid it would be a different, more expensive, driveline assembly (I would be VERY happy to have Lexus prove me wrong on that point). Anyway, I did not have the clunk until around 22K miles on the truck. The clunk occurs randomnly, but typically, after a hard stop. It feels like a 2 stage stop, one for actually stopping, and the second as a clunky settling of the truck to the "at rest" position. Sometimes the clunk is slight, and sometimes it really hits hard. The dealership aknowledges the clunk, but state it is inherent in the design. They will not do anything to correct it unless the directive comes from the factory. I am not sure if ALL dealerships take that position, but the one I go to does.
I had a secendary clunk issue with a sticking piston on the KDSS system. But, that seems to have been corrected. I think my next issue to address is the horrid braking system on the truck. I have read posts here and at another site, which detail how more than just a few have warped brake discs. But, that is another thread .... ;)