I hear that Ron Fellows / Spring Mountain does all of their extra 2qt's of DCTF fills via the air breather for the DCT. You can see the tube just to the passenger side of the throttlebody and "zip tied" to the back of the airbox.

I really wish I could fill mine this way, however I want a "record" at the dealer that their service team installed the 2 qts per GM specifications to avoid any sort of potential "warranty" issue with the DCT.
I would rather they not tear apart the trunk and potentially damage something, when the air breather looks super easy, but unfortunately that would give GM an out since I plan to track the car this year.

 

What are the parts outlined in blue and yellow?

 

heh, I stole another pic I found online and just added the red text showing the DCT air breather location.
The blue and yellow stuff is unrelated.

It seems a lot easier and less likely to cause any damage to me to just fill via that air breather line. Just need a funnel and a little more patience for the pour, but certainly faster than taking apart the trunk and air box.
Supposedly Ron fellows hasn't experienced a DCT failure, and they are obviously pushing them harder than a daily driver. What I want to know is how often they are changing out the DCTF fluid?
I believe you are supposed to replace the filters and fluid after ~24 hours of track use, correct? If they had to tear apart the trunk routinely, that would be silly stupid. Wish GM would bless this approach with a field notice.

 

^^^
FWIW, I suggested (if Tracking) in a June 9, 2020 post, rather than "take the car apart," just jack up the driver's side. I guessed 13 degrees (SWAG) and someone did it a few months ago, posted a video and it worked. As he said MUCH faster than messing with the Trunk, which he had done on another C8. He started with ~13 degrees and as I would have done, jacked it slightly more to get the full extra 2 quarts in. Measuring pic from his video it's about 15 degrees. The pic is from his video AFTER it was filled. URL is his video.

 

Yeah, I have seen that method too. I think the breather method is the easiest by far because essentially it is the same as just attaching a line to the top of the DCT not far from that fill plug.

My concerns are what if the breather tube has some contaminants in it, or voiding warranty.

 

Just jumping on the speculation wagon here, but coming from off-roading where a great deal of time is spent at weird angles, my crawler (4 speed auto) will lose prime and slip with the correct amount of fluid. A couple extra quarts of ATF and everything was happy. I have had the same issue with wet sump engines as well. Nothing like seeing the pressure guage drop when trying to crawl up the side of a V notch.

Anyway would make sense that tracking will see G forces be similar to a high angle situation and potentially lose prime/pressure. I would be hard pressed to see how this could happen on the street as you don't pull a continuous G force in any direction other than hard stop/starts which my guess the transmission handles these pretty well with normal fluid levels. All that being said, if they say it won't hurt anything, why not? I like the method of taking off the wheel and jacking it up. Simple and doesn't require pulling a bunch of stuff apart. That was a good way to overfill T'cases and diffs on off-road trucks for the same reason.

 

This is an easy way to do it. You need to add in steps and allow the air to burp out between fills.

 

That "logic" is what I initially thought BUT GM has NOT said that is the reason! Even Tadge (the Exec Chief Corvette Eng.) said it does reduce mpg (somewhat.) In my case don't care about mpg but do the extra drag higher fluid level causes.

This is from another of my posts with bottom pic added:

Been following the issue before I got my C8 in September 2020. Along with others have "speculated" why GM "probably" recommended adding for Tracking! GM has not said why! One well known YouTube posted said "he heard it was that GM found someone doing sustained donuts"- assume like a NASCAR winner! Foolish but would match what I thought "might be" the reason, high lateral "g" force causing fluid go go away from the oil pick-up. BUT GM has not said that is the reason. And my early Z51 Vettes did not have a dry sump and did hove special pan baffles (patented) like drag racers that kept engine oil under the pick-up! Been done for many years. The ONLY thing I have seen from a GM rep was quoted from a Carlisle Event where there was a talk and the rep said it was added if your Tracking going downhill the fluid will go to the top of the case! Since I don't "jump" by C8 not a credible reason to add!

Tadge said the extra fluid reduces mpg somewhat (due to increased drag with gears running in more fluid.) Also a knowledgeable Tech posted he had taken like ~50 DCTs apart for various reasons with and without the extra 2 quarts. Said there are many sensors, including 3 pressure sensors that will prevent damage if the pressure is several areas is insufficient. He stated several time in his long post NOT TO ADD UNLESS TRACKING. He showed there were like 100 CEL codes it will generate to protect itself!

Here are pics that also make me NOT add as I drive aggressively BUT don't Track. No "sustained" high "g" turns. Yep hit over 1 "g" lateral acceleration for short time BUT not sustained and I don't make foolish Donuts! WHY ADD If GM doesn't say to add other than is Tracking. I'd add if GM said to BUT NOT because some folks think it's a "good idea!"

Geared transmissions are NOT designed to have the gears in more than a low level of fluid!


The pics were taken from a good video by Banks who were designing a larger dif cover to hold more fluid to reduce max temps. The shape was very critical so as speeds increased excess oil foam was not created. Foaming oil reduces it's lubrication ability.

Only "semiofficial" reason given by a GM rep was at a talk in a Carlisle Event. Rep said if Tracking where you are making a turn going downhill the fluid could to the top of the case! So unless going down the Corkscrew at Laguna Seca or "Jumping" your C8 no compelling reason if NOT Tracking! There because GM recommends. I make many 1+ 'g' turns, albeit not sustained, and zero CELs or DCT issues. Have no plans to jump by C8!