I was wondering if the clutch is in neutral when sitting at a stop light? If I lift my foot just a little when stopped, brake light still on, I always feel it pulling the C8 forward. Is the clutch disengaged when stopped?
My thought was if it’s a manual trans, with a clutch disc, maybe I should put it into neutral when at stop lights to prevent the clutch disc from dragging and reducing the amount of disc debris.
If you have tech info you can post, please do.

Thanks
2024VETT

 

It does not go into neutral at a stoplight, the clutches keep a slight drag to mimic how a regular automatic transmission feels/behaves. If you pull back on both paddles, it will release the clutches to put the car effectively into neutral (I will sometimes do this when sitting at a long light for the reasons you mentioned). Tadge actually mentioned doing exactly this at one point, as well.

 

The DCT is in gear at a stop. Pulling back on both shift levers will put the transmission in neutral. Just drive and enjoy your car and don't worry about disc debris.

Kracka, you beat me to it.

 

I worry about disc debris. Trying to prevent excessive buildup in the filter that might cause filter bypass before 7500 filter change.

 

I have been pushing the N at known long stop lights. I will try the “ pull paddles “ method to see if I like it better.

Thanks

 

The clutch seems to be slightly engaged even with the brake on, in gear. With your foot on the brake, you move the gear selector between D and N or D and R, and I think you will feel it "take up drive line lash". But, when you take your foot off the brake while in gear, you will notice that the RPMs increase slightly, even without putting your foot on the throttle. I believe at this point the clutch is starting to engage a bit more than when your foot is on the brake. And yes, it does a good job of coasting like an automatic. I do not worry about the slight drag with foot on the brake, and do not bother with the double paddle declutch. My opinion is you could sit at idle, in D, with foot on the brake for a 100 hours and its not going to put as much wear on the clutch as a single launch. The manual says this about the double paddle declutch - "Use of Double Paddle Declutch on public roads could result in exhaust noise in excess of local laws" - which suggests its intent is so the engine can be revved up while stopped (at a light for example). It can also be use to initiate a "rapid exit" as described in the manual, as a way to rapidly reapply engine power to the wheels to support spirited driving. There is also a way to initiate a "manual launch" from a double paddle declutch. In the 2023 manual that feature says "Z06 only". But in the 2024 manual, that "Manual Launch" feature is not limited to the Z06.

 

Adding to post 6 - it is possible for a wet clutch to transmit some torque without physical contact. There is a "fluid squeezing stage" transmits torque entirely by hydrodynamic torque of the transmission fluid. In the boundary stage, torque is transmitted by hydrodynamic torque of the fluid and asperity contact torques (asperity contact referring to the peaks on the clutch surface, so now they are physically touching to some extent). In the third stage its entirely through asperity friction torque. I do not know the clutch engagement stage at idle with foot on the brake, but its possible that very, very little wear is involved. Here is the excerpt from the paper on wet clutches:

"the wet clutch engagement process can be divided into three stages [14]: the fluid squeezing stage, boundary lubrication stage, and mechanical contact stage. In the fluid squeezing stage, transmitted torque is composed of hydrodynamic torque of the automatic transmission fluid (ATF) oil film. In the boundary lubrication stage, the transmitted torque is composed of hydrodynamic torque of the ATF oil film and the asperity contact torque of friction pairs. With wet clutch engagement, contact pressure and friction torque of asperities gradually play a dominant role. In the mechanical contact stage, the transmitted torque is only composed of asperity friction torque. "

Here is the link to that paper about wet clutch engagement:

https://www.hindawi.com/journals/sv/2021/5522998/

 

Thanks Andybump

 

It's in 1st gear when stopped, you can tell by the display! However it's apparently at very low pressure IF you keep your foot firmly on the brake. Pressure increases with reduced brake pressure AND you can see the rpm increase. It does just what you would do with a standard shift.


I thought about the 1st gear clutch slipping when going very slow. It has to or like a standard shift the engine would stall below ~5 mph. So year one, with ~3000 miles I used the free DCT filter (that requires a flush) and engine oil change.

Just did my 3rd year all DCT fluid replaced and did a new DCT filter (with required flush) to meet the 7500 mile requirement. Since many folks reported DCT CELS early thought getting ride of early debris, especially from that 1st gear multidisc clutch was smart!

BTW, if you won't hit 7500 miles by year 2, foolish not to have it changed year one. GM says if you have it changed say year 2 with 6000 miles MUST change again at 7500 miles. Only +/- 500 miles allowed to deviate form 7500 mile required filter change. Would be silly to change at ~6000 miles to get the free new filter and again year 3 when you reach 7500 miles.

No issues with my DC in 3 years (looking for wood!)