Thank you for explaining G-Man!
Now that I understand what might be the clunk problem is, now every thing is clear why whenever I come to a full stop (not too slow and not sudden or abrupt). I feel some weird movement coming from the lower back to the lower mid-section of the truck. I thought some thing is wrong with the transmission not down shifting smoothly.....somewhat like a vibration in the lower back. It's annoying and feels like a big defect by the car manufacturer.
So, I'm going to my local dealer for them to replace driveshaft and control arm (if needed). I will post it here when the dealer has fix this issue.
Any way, mine is a 2007 GX 470. I bought it two weeks ago as CPO with only 2,500 miles on it.
Thanks for all your help and contribution to this wonderful and helpful forum.