For peace of mind, you can change the differential fluid at 60k if you want. It's subjective, but I usually change mine at 60k intervals. I don't think going 100k will hurt anything since Mercedes does not even have a formal recommendation on ever changing the differential fluid.

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Ali Al-Chalabi

2001 CLK55
1999 Dodge Ram 2500 Cummins Diesel
2002 Harley-Davidson Fatboy
Merlin Extralight w/ Campy Record