I'm sure this has been covered on the site, but I am new here and just curious about this problem.

Anyone found a solution?
I have an 03 and my brother has an 02. We both have the same issue. Other than that the truck has been great to us so far(knock on wood).

Need more info,
Just when do you hear these sounds?
What else is going on, speed, bumps, brakes on or off, all of the time, cold, hot, When you are loading your wifes purchases from her shopping weekend and then you notice you have a headache?
hahahehe,
humor....
Really now more info please.

Sound Like Its Coming From The Tailgate Area. There Is No Specific Time...just Happens When U Drive Over Any Surface

I would think that its the Rear Upper Control Arms, its a common problem amongst x5's.
I had mine replaced...out of warranty , did my self, on a scale of 1 to 10 its about a 5 in degree of dificulty.

If its under warranty have them change the upper sway bar links in the front as well and the CV boots shlould be looked at also.

Yeah BMW X5 i have a low tech way to fix the sounds coming from the rear upper door that knocking noise you here, whenever your driving or pass over a bump in the road....Know Open the rear upper swing up door, looking down to the lower door you will see the cross lock, now take black electracal tape RAP IT 3-4 times around the lower cross lock, which the upper lock catch into, after that open and close your upper swing door 1-2 times. make share the lock still locks and open as normal..... that it no more noise from the rear,...enjoy

Take it to the local dealer or garage they can help u with that.