Thanks Bucketoy. To hopefully better finish off this topic, I've found in the MidEngineForum, a thread where "Teamzr1" identifies the DCT fill plug on the side of the C8 transmission with the red arrow below in the larger diagram (ignore the black arrow; see comments below):
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Then "DCTguy" from that same Forum, better describes what you're seeing as follows:
Sorry I'm a bit late seeing this, but I want to offer some clarification so there is no more speculation/guessing.
The picture I grabbed from above has some great arrows in it so I will go off the color of those.
Blue - This arrow is pointing to the lower cover of the high pressure filter. There are four bolts to remove that cover. Inside is a cartridge filter that is changed as part of normal service
Red - This is actually the fluid level/fill plug most people will use. You fill the fluid to this level (until it starts to run out) then reinstall the plug. You fill it like you would a
normal manual - with a pump from below, or a hose from above.
Green - these are the electrical connectors. Not to be removed for any reason obviously
Black - this is NOT a fill plug of any kind. It is a detent assembly for a shift fork. There is another on the bottom side of the rear housing. Do not remove either.
The comments on the gold plug [see smaller diagram above with pink arrow]- The gold plug on the top of the main housing is the hole through which the transmission is filled at the factory. It is also a good option for adding the additional 2 liters for hard track use, though I believe air box removal may be required to access it. Another option may be to remove the rubber hose from the vent tube and attach a separate hose and fill through there. It would be slower to fill due to the smaller diameter, but would require less removal to access it.
Drain Plug - The drain plug is actually in the sump pan and not visible from this angle.
And everyone says be careful not to remove the wrong bolts or strip anything; it could prove costly. So map everything out in advance or forget all this and pay your dealer to do the work. Hope this helps out.
