Well, I did search the WIS, and there is NO specified interval.
On the G's, there IS a recommended interval of 60,000 Mi. Granted, it's under much more strain than the E, but it's the interval that I feel is "reasonable."
To me oil is cheap, and it's easy to change, so why not?
Also, the spec sheet now allows sythetics for diff's.
For some strange reasons, I can't find drain plug torque value in WIS. I saw references of 50 NM (36.8 pound foot) for filler plug.
When I changed the differential fluid on my 2001 E320 two days ago, I used 50 NM for the drain plug and it matched the original position that I marked before I removed the plug. I did not go any further in fear of stripping the thread. I sure don't want to pay the dealership to replace the differential for a stipped thread. I'll watch out for leaks though.
80 NM equals to 59.0 pound foot. That's a lot of torque. I wouldn't torque it that much.
50 NM (36.8 pound foot) is a reasonable torque for that size of plug. The filler and drain plugs look identical to me. I wonder why WIS specifies different torques for the same size plugs.
BTW, the original differential fluid (35K miles) are so dirty, it looked like mud. I'm so glad that I changed it.
Personally, I will change it every 30k miles. I don't understand why MB does not specify the frequency of changing this oil.
I have low miles (35k miles), so, I did not notice any change of noise. I changed the oil because I want to keep it in a good shape, not because there was a problem.
I ended up with Mobile 1 synthetic. I was very disappointed with Mobile 1 though. I used a clear vinyl tube extended outside of the car. So I was able to pour the oil into this tube and was able to see the oil while it's being fed into it. Occasionally I saw "air bubbles" in the fluid and did not mind with it. However, when it approaches the end of the bottle, there were tons of "air bubbles". That made me aware that they were not air bubbles after all. They are contaminants. In other words, mobile 1 synthetic has debris at the bottom of the bottle. However, I tried to use my finger to feel the "hardness" of these debris in what were left in the bottle and can't feel anything (They were visible though). I guess they're harmless. But I'm very disappointed with Mobile 1. I will try Red Line next time. Maybe I'll use MB's oil even though it's much more expensive.
I used Permatex High Temperature Thread Sealant (Part number 59214). It's available at Autozone. MB's Omnifit Sealing Compound 100H (A 003 989 18 71 10) is available at the dealership via special order (House of Imports, CA).
I was not able to find any reference of the torque value for the drain plug. Could you provide a pdf/word or just a screen capture of the document? This way, I can understand whether I under torqued it or not. I hope it's not too much trouble. Thanks.
Great write up, I plan to do mine soon. Does the S430 also use 75W90? My guess is yes..
One point I would like to add. Always loosen the fill bolt first. If for some reason you are unable to loosen the fill bolt and all the diff fluid has been drained out then you have a real problem on your hands with an empty diff. Same applies to 4WD transfer cases.
If the bolts were torqued to spec and not cross threaded then there should be no problems (Murphy's Law). I did my MDX and had to use a rubber mallet on the ratchett to loosen all for drain bolts. I almost had to resort to my air impact wrench. They were way beyond the 33ft/lb specs.
W210 Differential Oil Interval 
Linear Mode
