Even if you don't plan on tracking your car?

 

I think I will probably add it after the initial DCT filter change. It certainly couldn't have negative effects. This would also help the DCT keep lubricated, especially when you plan on using the Launch Control option every so often.

 

I had my dealer add it during PDI; I do not track my car. The transmission has been flawless for 7k miles and just had the 1st filter change last month.

 

Anyone know what the inner diameter is for the DCT upper fill hole that's underneath the air cleaner? I'd like to create a DIY funnel and flexible tube combo for this purpose.

 

I added 2 quarters to the transmission by jacking up and removing the rear driver side wheel. The bottom of the rotor should be about 16 inches off ground. Ran a tube to the lower drain plug and filled. Piece of cake and didn’t spill a drop. Took 20 minutes.

 

My car was built Wednesday. Estimated delivery to my dealer is Tuesday Dec 7th. Asked him to add the 2 quarts during PDI even though it's NOT a z51 and I won't be tracking it.

He said the Corvette techs there are afraid to add it during PDI because adding it could potentially DAMAGE the DCT.

I told him that's absurd. While the extra 2 quarts isn't necessarily needed and may be a waste of money, having it in there certainly wouldn't HURT the DCT. More fluid means it would take longer to heat up, but other than that there is no reason I can think of that the extra fluid could in any way damage the DCT. It would be one thing if you were OVER filling it, causing too much pressure once the fluid heats up, but if the DCT can safely hold the extra 2 quarts for track duty, it can certainly handle it during break-in.

At the risk of getting a 5 page reply and diagrams of rural roads, can @JerryU chime in on my assessment above? I don't care if I'm throwing away $$ on unneeded fluid, but I'd like to know if their corvette tech has any basis for making such a wild claim about risks of adding it.

 

^^^
Sorry for not understanding your PM question. Here is a 3-page response to "adding the 2 extra quarts."

I did not and will not add until GM specifies why! So far it has been speculation, including my own re why GM says add to tracking. Some say cooling and if that were the case 2 more quarts to the 12.6 standard fill won't do much but delay how not it gets. The DCT has a large liquid to liquid cooler and not any significant mention of overheating. With my street driving even when most is Powertrain set to Track it's not an issue. PLUS GM never said that is why it's added.

I speculated it was for high "g" turns where the fluid MIGHT not get to the pick-up. That was supported by a YouTuber who said GM added because they found someone doing foolish "donuts" (assume like a NASCAR winner!) BUT GM has not said that is the issue. In that regard there is a tech with lots of experience with DCT's who said there are 3 pressure sensors and 100 codes that can be tripped if something is not right. He said strongly don't add if not tracking.

The only semi-official reason I have seen is at Carlisle PA there was a talk by a GM rep who said it was added if when going downhill and making a turn the fluid can rise to the top of the case (assume away from the pick-up!). However, looking at where the fluid is (see pic) that may help a little but at Laguna Seca going up and over the Corkscrew it could still go to the top.

Your car your choice BUT I can't see it will hurt. It will increase drag and IMO since I have not heard a good reason for my street driving, extra drag with gears running in more, deeper fluid is not a good thing! Tadge did say it will reduce mpg somewhat.


Note where the fluid height using the fill plug. Adding 16% more height is not like filling the case but will increase drag!


Unless planning to go on a downhill turn like the Corkscrew at Laguna Seca or Jumping your C8 have not heard a compelling reason to add for street use!

 

Appreciate the response @JerryU . As it turns out there are some pretty steep downhill turns in the TX hill country twisties!

I have no intent of jumping the car, but some of the turns on downhill slopes here are pretty hair-pin. Given that possibility, I would think it would be a good idea to add the 2 quarts to prevent just such a scenario as the corkscrew turn pictured in your post. Thoughts?

 

Hard to say. That DCT knowledgeable tech who as I recall had looked at many internals with and without the extra 2 quarts said there are many sensors and 3 pressure sensors that if a problem occurs will trip a CEL and help avoid issues. he said several times in his long post (longer than mine) not To add unless Tracking.

 

Appreciate your replies, and hope you know my comments about the length of your post were in jest. Newcomers to the forum get good info from them.

 

I did not have my dealer add it during PDI; I do not track my car. The transmission has been flawless for 7k miles and just had the 1st filter change a couple months ago.

 

^^^^
Yep, I'm the same, don't Track so no added (have not seen a compelling reason to add.) Had my 12 month service end August that included DCT flush prior to filter change. Trans perfect.

 

The fluid will not go to the top even in a 0G environment since the car and the fluid will be falling at the same rate. It will "float around" inside the case and may uncover the pickup but that will be a brief occurrence.
The worst case is probably a low vertical G environment while rounding a corner (like the corkscrew) that would cause the fluid to go to one side of the case and uncover the pickup. That is where additional fluid may help enough to keep the pickup from being uncovered.

 

^^^
Yep, agree. The GM Rep at the Carlisle Event apparently ONLY mentioned that situation; a turn on a downhill! Not many turns like the Corkscrew at Laguna Seca.

Brought back memories of my friend Tom who had ~40 vintage cars (most restored race cars and had a similar number OF restored vintage Great Lake racing boats.) Born the same year as myself and died unexpectedly 11 years ago. Pic below I took at Laguna Seca of Tom in his Maserati Bird Cage going down the Corkscrew, Have the pic in my man cave along with some 50 cars I bought after he died (most of mine are CMC Models!) Also have a 36 inch long model of the 1924 Baby Bootlegger with WW I aluminum Spanish airplane engine that was one of many on display at Tom's celebration of life!


He also would bring this restored Cunningham that ran at Le Mans, to Laguna Seca! Funny as compared to the light Bird Cage it was very heavy and really not fit for Laguna Seca. He'd be in the lead of a pack going down the Start/Finish Straight and soon after the Andretti hairpin, last! Recall asking why didn't he get better brake shoes and he commented he wanted to feel exactly what the driver's of the era felt. All tires where matching vintage rubber!

 

Going back to the DCT fluid, how much is lost during every filter change? Maybe enough to justify adding at least 1 quart after the first change instead of the 2, perhaps?

 

4-6oz seems to be the generally accepted volume. If you're going through the trouble of adding 1 extra qt, Just do 2. Zero downside other than the cost of fluid (unless you're concerned about losing .01 MPG).

 

For what it's worth, I just had my 1st service done, as well as a High wing spoiler install. I spent a bunch of time with the lead tech and asked if he could add the 2 extra quarts. His response was unless you are tracking the car regularly, GM is advising against it. Again don't
shoot the messenger, I told him I know this is a big job and I would take care of him as well as the normal hours billed and he insisted, unless your tracking regularly "DON'T Do It" ... At one point in our conversation, he even said he thought he recalled GM advising removal
of the 2 quarts if you returned to primary street use. This is coming from a 25+ year GM "A" tech.... I don't know what to believe now.... When I picked up the car, he came out and met me and said I put 3 quarts of DCT oil in a box in your trunk, he said they were all nearly full
minus about 8oz, which is what they use on the first service and filter change... I appreciated the gesture and of course the freebies.... I just don't know what to believe anymore.... Long story short, I elected to not add until I can get more info....

 

^^^
Yep, have 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!

Frankly although your Tech said GM recommends removing, Tadge said although the extra fluid reduce mpg somewhat (due to increased drag with gears running in more fluid) it's NOT required to remove after Tracking. Also did not see GM every saying not to add BUT 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 sated 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 two pics that also make me NOT add as I drive aggressively BUT don't Track. No sustained like high "g" turns. Yep hit over 1 "g" lateral acceleration for short time BUT not sustained and I don't make foolish Donuts! Your car but consider WHY DO YOU WANT TO ADD1 If GM says to add (like they do if tracking) I'd add BUT NOT because some folks think it's a "good idea but have no reason!" IMO, as Chuck, Rick Conti's Tech showed all Thermic had to do was put the add plug about a foot further back on the case. Appears to me to be an afterthought, for whatever reason!

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.

 

That is incorrect. The track prep guide along with Tadge himself both confirmed their is no reason to remove the fluid. Very nice gesture on the mechanic's part though to give you the fluid at no charge to do yourself! Not including the fluid from the factory was a cost-cutting and MPG play that will be corrected for the Z06's release.

 

Great post thank you, very informative!