I have been searching the archive for the procedure. Here are the conclusions and questions I got:

1. I guess I found the drain plug. It's a plug that can be turned with 14mm allen wrench.
2. Where is the refill plug? What size and type of wrench should I use?
3. It is advised to clean the vent on top of the differential. Does it hold true for my car?
4. Should I lift up the car to gain access under it? If yes, driver side or passenger side is prefered?
5. Any other tips am I missing?

Thanks.

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Harry (94 C280)

If you lift the car, lift the car opposite side of the drain plug, then lower before filling. You want it level to fill. The fill is on the other side up high. About 3/4 the way up on the side. Be sure to use a high quality lube. They sell a good lube at the dealer.

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Benzmac:
1981 280GE SWB
1987 16V
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

A little hint:

Make sure you can open the fill plug BEFORE you drain the old oil out.

Been there. Done that.