Hello FTE.

I am a first time diesel buyer who just bought a 2011 6.7 with ~175,000 miles on the clock.
It is bone stock with a clean carfax and regularly serviced. I had the oil and filters replaced including fuel filters, and had an inspection done all by a trusted dealer. They noted the only issue seeming to be some "oil seepage" (unspecified location) and to keep an eye on oil level.
However, I am aware that things can be missed and these vehicles aren't infallible, so I pose my question.

After purchase and having driven it for around 800-1000 miles I noticed some leaks developing around the bellhousing of the transmission where it meets the engine as well as towards the rear of the transmission pan.

This usually appears after it has parked for a little while (4 hours ish) as seen in this image:

This is the rear of the transmission pan (note: I have not seen this drip on the ground, only some seepage around the seams):

This is the drivers side where there is clear oil residue:

This is the passenger side (the circled area was still wet):


I have been told a number of reasons for this: crankcase vent, rear main seal, upper oilpan gasket, turbo leak, etc.
I was originally inclined to believe it was the upper oilpan gasket until I really began to look at the details.

When I shined a light into the engine into the Vee around the turbo I saw a lot of black in the valley, not a good start....
Then I realized that there's this card-in-bicycle-spokes kind of noise coming from the engine (best way I can describe it). Listen for yourself in this unlisted video:
This very well could be a normal noise for a non-deleted 6.7 with the GT32 SST turbo and I could just be paranoid over a bad gasket, or...... the turbo might be going out.
I know the early turbos are failure prone, and the evidence given to me with my limited experience in this points towards the turbo, but I ultimately don't know.

I am hoping that the experts on this forum can give me a more precise answer than my frantic google searches, and I appreciate all responses.

Thank you,
J