2023 HTC.
It ius said to add 2 extra quarts of tracking/ racing.
I street drive, yet race on/ off ramps

Seems the only negative of adding 2 quarts is fuel economy.
Since I don't do sustained corning, I was thinking of adding only 1 extra quart.
Remove wheel, tilt car, add oil.

Thoughts from my co-member please.

 

Lots and lots of debate on this. I track my car '23 with the old style sump pickup and therefore add the two extra liters. For your use I wouldn't do it especially if your car has the updated sump design. Will it hurt the DCT, no. Will it help, not likely.

 

When was your 2023 built?

The change over occurred mid- MY so whether to do it at all starts with that. If your VIN is 37263 or higher you have the newer design and DON'T add the extra quarts.

 

My '23 VIN is lower than 37263.

 

Add two extra liters if tracking. Don't if not. Worry not.

 

It is an extra 2 liters in the DCT TRANSMISSION not the engine if you have a 2023 or older car.

Corvette engineers said it wasn’t necessary.

If you want to overfill your engine by a qt or two keep us posted.

 

Here is the complete statement from Josh Holder about the 2 liter overfill for track use on 2023 or earlier model. It was in the context of the change in late 2023 that negated the need for the track fill. He did not go so far as saying not to do it for track use - he said they might have done it differently in retrospect. But he also said it was for "extreme" cases. It is very, very unlikely to encounter that condition in street use. One might consider though, that if it was really not necessary for track use, they would not have made the changes to case and pan. Some want to add the 2liters or some extra for street use anyway - and cite various reasons (such as perceived smoother operation or cooler fluid, or just wanting to insure it at or above the required level or...?). No problem. But for street use its not going to be about uncovering the fluid uptake point in the pan.

Josh Holder - in response to questions about the changes to the case and pan for the die 3 transmission that negated the need to add 2 liters for track use

"Q: Are the two additional quarts (sic) already there?

Josh Holder: It’s not really the case [meaning no]. The case is, literally, changed for ’24. We did it because the Z06 necessitated a change in the lube system. Where we keep all the critical oil in a car on a Z06 that has so much lateral capability, was super important. So knowing that we needed to change the case and update the lube system for the Z06, in 24 model year, actually very late in 23 as it turns out, we moved all Corvettes to the same differential, err, the same transmission housing that the Z06 has. And when we did that you no longer need to add the additional 2 liters of oil. That [referring now to the 2 liter overfill] really was a way to keep (the) lube system healthy, lubrication where it needed to be, but it was overkill, it wasn’t kind of the way we would have done it starting over.

Q: Is the pick up point different – is that what it is?

Josh Holder: The pick up point is not really different. What is different besides the the size and shape of the case itself, which can hold more oil near the pick up point. But there’s baffles inside the transmission that under high G loading keep the oil near the pick up point, which is the whole goal of (the) lube system. So that’s the benefit that all Corvette receive in 2024 models.

Q: what if a guy (sic) did put the two additional quarts (sic) in there?

Josh Holder: In the 2024 transmission?…You could do it, actually you might risk some expulsion through the vent tube. It would be a wasted effort. So, I would not recommend doing it in a 2024. And honestly, when we recommended it in 2020 it was for a really extreme scenario, and in hindsight, I’m not sure we would’ve made the same recommendation. Its not easy to do for those that have done it themselves, a I’ve done it myself. Its not super easy. And so, we’re really glad that we got to take that revised lube system strategy to all Corvettes. And now anybody that wants to tracks their car or don’t track their car doesn’t have to worry about whether they have to add two liters or not and am I going to be that person that drives so extreme, maybe I need two liters, maybe I don’t. Takes that question out of it."

 

When I did the drain and fill I added extra, about a liter and a half. 2020. I felt a noticeable difference in how smooth the DCT felt. While maybe not needed it was no extra effort and minimal cost.

 

Thank you for all the comments.
I am unsure, yet am still open to add some overfill amount.
Again, I may not do 2 quarts, yet 1/2 to 1 seems to make "dependability" sense.

 

It should have no effect on the feeling of the transmission. Clean lube and/or filter might be the more likely reason for the better feel in my opinion.


A forum member had issues with the additional fill. The fluid slushes more inside, and it caused a transmission overheat false signal, slowing the car down in one of those 1 mile top speed competitions. GM engineers were the one who found out the issue (of why the car was not consistent in the event). The engineers also said even for most track use, it shouldn't be necessary, but it's a precaution for tracks with a sudden dip.

As such, in street use, regardless of how you use it, I don't think you'd need it at all in my opinion..

 

Agree its not needed for street use. Its not required by the manual of any model year and GM reps have stated the same. We we also know from the track preparation instructions that come with each model year that once it has been added it is not necessary to remove for street use. Both things are true. It not necessary for street use, but its also harmless.

The specific issue with overfill that caused the erroneous heat signal and resulting speed limit was for sustained high speed use. It was specifically 6th gear that was actually spraying hot fluid directly on the sensor of concern, while the average temperature in the pan was normal. This will not happen in street use.

https://www.corvetteforum.com/forums...-engineer.html

While its not necessary for street use, others have also reported smoother operation. I think its possible (emphasis on possible) that it does make it seem smoother (and I am not even saying smoother is better or worse). The reason I think that it may make it smoother is the additional fluid may provide more "viscous" damping as the clutches engage. We know that Tadge and other GM engineers have stated that the additional fluid will reduce fuel economy because additional drag due to the excess fluid which suggests that additional fluid is being carried by the transmission components. I do not think it has any affect on the actual fork movement and gear changes - we don't feel those anyway. What we feel is the clutch engagement events, which might be affected by additional fluid around the clutches.

Josh Holder did state the overfill was for an extreme case of track use and in retrospect they might have done it differently. But he stopped short of saying that you should not do it for track use if you have a 2023 or earlier model year. And also, if the overfill was really not necessary for track use, then why did GM modify both the case and pan in the Stingray transmission so that the overfill is not needed for those transmissions?

 

Right on Kenny: When my 2023 was new I added 2 quarts. More fluid equals less contamination per quart.
Now with 10K miles, and coming up on the three year required change, I may add one extra quart this time.

Remove wheel, tilt car, add oil. That is the easy way to do it.

 

Interesting perspective.

This would refer to particulate contamination that is not removed by the filter, I assume? Whether its 11 liters or 13 liters, every drop flows through the filter, the lines, valves, and hydraulic actuators pretty quickly, so larger particulates are removed by the filter and do not accumulate in the fluid. Particulates small enough to pass through the filter will accumulate. I think it is true that if debris is being shed (and it is) some portion of it is going to be small enough to pass through the filter, so it will accumulate., though I have no idea how much of that small stuff accumulates between normal filter change intervals. The concentration of those smaller particulates will be reduced by about 15.4% with 13 liters vs 11 liters.

((Paccumulate/11)-Paccumulated/13))/(Paccumulated/11)= .154

Where Paccumulated is the amount of debris in the fluid that is not removed by the filter, and concentration/liter is Paccumulated divided by the amount of fluid (11, 12, or 13 liters).

With 12 liters instead of 11 liters, the concentration is reduced by 8.3%.

So, it will reduce the concentration of the smaller particulates that are flowing through the lines, valves, and hydraulic actuators. It would also reduce the concentration of chemical contaminants, assuming they don't come from breakdown of the fluid itself.

 

Andy, you are a real scientist. What would we do without you.
My thinking: For X amount of clutch and metal contamination, you could distribute that in 10 qts of fluid, or 12 qts.
Yes, it is all filtered, but not everything gets filtered out. For the remaining contaminates, I choose to spread them out into 12 qts.

When I bought my 2023, I asked a Chevrolet Service Manager if there is any reason to NOT add 2 extra qts.
"Cost". It can't hurt, maybe it will help.
I'm not going to the track so it is probably overkill for me, but it makes me feel like I have done everything I can do to protect the trans.

 

I think the best thing you can do is changing the filter more often, and changing the fluid, too, though probably not as often. Without that additional 2 quarts, changing is much easier (1/4th the time), so if it enables being able to change more often, I think it'd be more worth it. Many folks who had shifting jerkiness got it fixed after change of filter, which should be a good signal on how important it is. The casing is shared with the diff, so the fluid takes a beating for sure.

 

Why do you say 1/4 the time?

 

When you don't need to top it off, you can just use the bottom bolts to drain and fill. For that extra 2 quarts, you either need to remove the trunk carpet and air box, or tilt the car steeply and reach out from the wheel well; that's a lot more work.

 

Thank you. I added the extra by tilting. I had already taken off the rear drivers wheel for filling so it was just moving a jack and lifting to add the extra. Absolutely if removing the trunk it adds time.

 

Agreed that changing the filter often is probably the best insurance you can buy.
I only drive <4000 miles a year so my plan now is change engine oil and filter once a year,
and at the same time, change the trans filter every year. Change Trans fluid every three years.

It is easy to jack up the drivers side, remove the wheel to add extra trans fluid.
I can do that in 15 minutes. Working around that air intake looks like a real nightmare to me.