I just got the clunk week ago. I'm a little over 1,000 miles. Today, I had them re-torque the cab to chasis bolts.....I think he said there were four (mentioned on another forum to maybe tighten them). I feel it directly under my left foot, but only on turns......and not on every turn. Just a lil pop/thud sound/feel. It doesn't happen alot, but now I'm riding around with no music, purposely listening and feeling for it.
I think I heard it twice after he tightened things up......on my way home from work, I didn't hear it at all. I'll keep listening and feeling for it. I bet they come out with a service bulletin if enough of us keep taking our trucks in. On another site, some mention to check the sway bar mounts.