Single clunk noise under the car?

[Tn52]

Hi everyone:
I need help to narrow down an annoying single clunking sound from somewhere in the middle (and possible in the back?) under my car. From more than a year, I am experiencing this clunking noise especially when:
1. Mostly when I turned left or right. I can easily reproduce the single clunking noise when I turn from the street to go up to my driveway. or going down from my driveway turning into the street.
2. Going straight then slow down/braking before a turn.

There is NO clunking noise when I accelerate, brake, or going straight (even on a bumpy road). I noticed the clunk noise only happened when there is a shift/twist of the car weight from one side to the other. My indie checked all the 2-3 flex disks from the drive shaft and they are ok. He does not think the sub-frame bushings are bad either.

my car: 05 X5 3.0L, no air suspension.
Thanks!