WTF is this grated area? I am curious about what the hell could be letting oil out of there...

I have no reddish fluid though, so tranmission doesn't seem to be leaking. I have no idea about this part of the car. I am curious if it is something this is fixable in a decent price range or what the hell it is anyhow.

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1976 300D
190,000 Miles
Colorado Beige

1975 300D
Parts Car
78,000 Miles
Rustbucket
Also Colorado Beige

1984 190D 2.2 (Dad's)
156,000 miles
Champagne Metallic Clearcoat