A noise is one of the hardest problems to find when you are there but almost impossible when trying to do it from afar. I would say to put the car back together and drive it. Listen for any unusual noises. Try very low speed with the doors open (in driveway) and listen for the noise. Next drive moderate speed (say 30 or 35) both with windows open and with windows closed. Try right and left turns. Next try highway speeds. Again, carefully try right and left maneuvers. All the above with the radio OFF, A/C off, and anything else that makes noise that is not necessary off. If you don't hear anything then drive it until it shows up. If you do hear something in any of the above test, let us know under what conditions you would hear it. I think it has been mentioned before but make sure the gear oil is the diff is clean. If it looks similar to metal-flake paint then start looking for a new one. Other than the above I can't think of any thing else at this time.

Based on what I have read in both threads and your description of the noise location, The only remaining possiblity is the wheel bearing. I have never replaced a wheel bearing on a MB, but I would think you may find some play or movement in the rear wheel. With the wheel raised and tire on, if you grab the tire at 12 o'clock and 6 and rock it, is there any play or movement? Try it at 9 and 3 positions as well. You should not feel any movement or play.

I did exactly as you suggested:

1) Very low-speed w/ doors open... That noise can't be heard.

2) Moderate-speed (30-35) w/ all windows open, left and right maneuvers... No noise. Then again with windows closed: no noise. I even tried, with all windows open, to take the car up to 40m/h, then put it in neutral and listen for sounds, letting the car slow down to almost a stop: all you hear is the wind, that noise doesn't show up (I guess it is covered by the engine noise).

3) Highway speeds: you can't hear anything there either.

I replaced the diff gear oil in February (two months ago), and the old fluid came out just like new... same exact color of the new one I put in, it even smelled just the same.

So, given the above, your advice is to just keep driving the car until something shows up...

Yes, that would by my suggestion. Others may have other views.

I tried that on both the rear left and rear right wheels (since I had to raise the rear end up to do it anyway...)

REAR LEFT WHEEL (the side with the noise):
When pulling back and forth evenly with both hands, no detectable movement in either the 12/6 o' clock and 9/3 o' clock positions.
When alternatively pulling with one hand and pushing with the other, no detectable movement in the 12/6 o' clock, BUT very slight movement was detected in the 9/3 o' clock position.

REAR RIGHT WHEEL (the side with NO noise):
Exactly as per the rear left wheel: same slight movement was detected in the 9/3 o' clock position when alternatively pulling with one hand and pushing with the other.

So, both sides are the same, but only the rear left wheel makes that (slight) noise.

Again, the noise I'm talking about is the rasping sound that happens when the rear end is up and I rotate the rear left wheel SLOWLY... In addition to that, there is another sound coming from the rear left wheel that takes place when the car has all tires on the ground and is pushed, either forward or backward... It is sort of a slight clinking noise and is detectable only when pushing the car by hand, with the engine OFF, coming from the rear left wheel. It is an intermittent noise, happening only very briefly at each full rotation of the wheel.

What do I do at this point?

OK. Thank you very much for your advice!

normal running 240D
 

My values are from my normal running car. I sure hope its normal as I'm now in florida after driving 1300 miles and at least that much to get back home.:D

That's great! I hope you are enjoying your trip... Has everything gone all right so far with the car, with no issues coming up during such a long trip? That's inspiring...
Have a safe trip back home!

As for me, I'll follow the advice given and, in spite of the noises described above, I'll keep driving the car as is...
If something should go bad, I hope there will be a gradual worsening of those signals to give me at least some time to take notice and fix whatever the problem is, as opposed to the thing suddenly breaking down totally with no warning...:juggle: