New unit was promised, but it looks like what I got was an "exchange aggregate" ger.-"Tauschaggregat". which had the part numbers ground off the case and an aluminum tag attached to show new part number. 140-350 63 14 and another number "Tiel NR 25 0455"
Perhaps this re-assembling of returned cores with (hopefully?, with new gears and bearings) is as close as can be gotten to a new part, with a 10 year old S class

I took 18 days to complete the repair... My dealer provided a rental-loaner car at no cost. I am really glad that Starmark fixed my car!!

But questions persist:

1. What caused the diff to go bad? I assume that the Prev. Owner allowed the diff to run low on lube. Dealer had re-sealed the diff only a few hundred miles before I purchased the car.

2. 500 miles after I got the car back with the "new" or "rebuilt" differential I decided to drain out the lube and install Mobil 1 synth. 75W-90 gear lube. While everything is very quiet now, I was puzzled to notice that only 500 miles had produced a marked blackening of the lube. I let the lube sit two days in the clean pan and the dark lube settled out at bottom of the pan. A very few bright (tiny mico sized) metal particles could be seen and the blackened lube would follow a strong magnet up into the clear top layer of the lube. That meant that the dark lube contained steel wear, right?
NO particle size stuff at all, and the replacement unit is very quiet.

3. Is that much wear normal during the first few hundred miles ?

4. Should I have left the "factory" lube in longer before changing to Mobil 1 synth. ? Looks like dumping out that blackened early wear lube has to be a good thing, ? Right?

Anyone have informed insight into any of this? I appreciate all posts and readers. thanks,
I have pictures of the lube, but it doesn't show up very well so did not try to post here.

DanielW