Thats good news for you!
I just bought my 2005 E320. I am hoping for a long term happiness affair with this car.
I am a maintenance freak, so I am hoping for good things. Mine was well maintained from new, I have all the records. Mine now has 149K on it.

 

One Thing....

There is one thing I somehow FORGOT to mention in my report: at about 75,000 miles I noticed some rear end gear noise, or what I believe to be rear end gear noise. I've changed rear differential lube a couple times, and the M-B spec fluid in it now seems to offer a slight improvement over the Mobil1 Delvac 75W-90 that I tried earlier. The noise also seems to be more noticeable in cold temps as opposed to warm weather. It does not seem to be getting any worse but it does vary. I have not found a "next step" to address it; I sure don't feel like buying a replacement differential assembly for $$$.

So, I am leaving it alone, and will see how things go. The noise is not severe and most people (e.g., the wife) probably would not notice it. But I felt that I ought to supplement this report and mention it, to give a more accurate picture.

 

There is one thing I somehow FORGOT to mention in my report: at about 75,000 miles I noticed some rear end gear noise, or what I believe to be rear end gear noise. I've changed rear differential lube a couple times, and the M-B spec fluid in it now seems to offer a slight improvement over the Mobil1 Delvac 75W-90 that I tried earlier. The noise also seems to be more noticeable in cold temps as opposed to warm weather. It does not seem to be getting any worse but it does vary. I have not found a "next step" to address it; I sure don't feel like buying a replacement differential assembly for $$$.

So, I am leaving it alone, and will see how things go. The noise is not severe and most people (e.g., the wife) probably would not notice it. But I felt that I ought to supplement this report and mention it, to give a more accurate picture.

It could be the transfer case or one of the rear wheel bearings.
Have you changed the TF fluid?
My car had a loud zipper noise at 100K miles, I thought it was the tires, once I changed the fluids in the diffs and TF, the noise was completely gone. I used Mobil 1 Delvac that I bought from a truck repair facility(cheap but BYOC) on the diffs and MB fluid in the TF.

 

Now that you mention it. I notice a slight whining noise with mine. But dont know where its coming from. They never said anything at benz during my maintenance check. And when I was at sheetz the other night. There was a E320 there. And when it pulled out. It also made that slight whining noise.

 

TC Done

Yep, I did the TC at ~40k and 90k using the MB fluid. In both cases it helped quiet the TC down somewhat, but that was a different kind of noise than what I am getting from the rear.

The front diff has Delvac in it (from WW Grainger) and sounds fine.

At the rear, I pulled the wheels, and could not find any signs of play or noise at the axle ends themselves. Inboard, though, there is some play in the differential (axle shafts have some slop) and I am pretty sure the noise is coming from that. It does not vary in R or L turns, as a bearing usually will, and is road speed dependent.

 

I suggest you drain the rear diff into a clean container after a long drive, look for slurry and metal shavings, it would be an indicator of a bearing and/or gear wear.