Rear-end Clunk when stopping

[SonofaBish]

I've had my 2007 X5 4.8 for only about 3.5 weeks, and i'm pretty happy with it so far.... i have a weird climate control issue that is annoying, but otherwise i love the car...

Another thing i have ran into - a clunk that sounds like its coming from the back of the car - it happens RIGHT BEFORE you come to a stop - doesn't matter if you've been hard on the brakes, or just lightly came to a stop, it will *sometimes* make a clunk right before the car comes to a hault (less than 5mph)... i don't think its the transmission, because i've manually shifted it to first, then braked very slowly, and still heard the clunk....

You can't feel it in the pedal - can't feel it in the car at all... can't even really hear it if the radio is on, but if you have the radio off, you can hear it pretty easily...

Also, it seems to do it sometimes when you go from Drive to Reverse, once you hit the gas, you will hear the clunk

Does anyone have any ideas?

It really doesn't sound like a bushing or anything to me, as i would expect that to happen when the weight transfer happens - not the case here... Differential fluid is good... so i'm kinda at a loss... It doesn't seem like something that is damaging, but I want to be as cautious as i can be....