About to dive in, weather permitting, and service the
diff on a 380SL. Set to go with correct fluid, I know
enough to open the fill port FIRST to be sure that it
can be opened, etc.

The great thing about this forum is the way that it
reminds one about small things. Dug into the archives
on diff fluid and found a reminder to clean and blow
out the vent on top of the diff. Before this I hadn't
even known it was there! You guys are amazing.

So while I'm aware of the vent and can see it, I am
not up on how it comes free. Someone's post said that
it loosens with a box wrench, but it looks round from
the angle that I have on it. Am I missing a trick here?

Ron H

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I know on the w123's you should be able to get a box wrench around the base of the vent plug. Its been a while since I serviced my diff, but I think the base is square. You might want to carefully use a small pipe wrench if its hard to fit a box wrench under there. Good luck.