Idle Creep
Thread Starter
Intermediate
Joined: Mar 2018
Posts: 45
Likes: 26
From: Georgia
Idle Creep
Just posting this as an FYI. Had an “Idle Creep” alert at 38,000 miles on my 2021 C8. Took it in and they couldn’t find an issue and just flushed the trans fluid. At 45,000, got the idle creep again and they are replacing the valve body on the transmission. I got 15,000 miles left under warranty so suffice to say if it happens again and they don’t replace the transmission, I’ll trade it in for ?
Drifting
Joined: Aug 2022
Posts: 1,900
Likes: 789
From: Stamford, CT
Very disheartening that this is happening on higher mileage cars as it has been touted as a fail caused by early mileage break-in debris. Yours must be one of the highest mileage C8 vettes out there. The good thing is that you have the issue documented. Other brands (BMW) will do good will repairs past the factory warranty expiration if the problem was flagged and documented by the dealer before the expiry.
Melting Slicks
Joined: May 2021
Posts: 2,562
Likes: 1,579
Very disheartening that this is happening on higher mileage cars as it has been touted as a fail caused by early mileage break-in debris. Yours must be one of the highest mileage C8 vettes out there. The good thing is that you have the issue documented. Other brands (BMW) will do good will repairs past the factory warranty expiration if the problem was flagged and documented by the dealer before the expiry.
Might have been better to isolate the clutch fluid from the rest of the transmission. The one item that for SURE wears and releases particulate matter is the clutch, throughout the life of the car. No matter what you do, clutches gonna clutch...Treating the circulating oil like a slushbox maybe a bad idea?
I know some people say they "pampered" their cars during break-in and still had issues with solenoids too, but I would be willing to bet there might have been a few "white lies" there. It's a performance sports car. People didn't buy it to drive it like a granny.
Problem is this means you need another pump and coolant loop, unless you could use some sort of internal heat exchanger.
I haven't seen a single "technical document" that discuss what exact material is fouling these valve bodies. GM is keeping us in the dark.
Race Director
Joined: Aug 2016
Posts: 12,812
Likes: 10,229
From: Garden Valley CA
If I had to hazard a guess, having a wet clutch running in the same oil bath as the dozens of solenoids and valves is a bad idea.
Might have been better to isolate the clutch fluid from the rest of the transmission. The one item that for SURE wears and releases particulate matter is the clutch, throughout the life of the car. No matter what you do, clutches gonna clutch...Treating the circulating oil like a slushbox maybe a bad idea?
I know some people say they "pampered" their cars during break-in and still had issues with solenoids too, but I would be willing to bet there might have been a few "white lies" there. It's a performance sports car. People didn't buy it to drive it like a granny.
Problem is this means you need another pump and coolant loop, unless you could use some sort of internal heat exchanger.
I haven't seen a single "technical document" that discuss what exact material is fouling these valve bodies. GM is keeping us in the dark.
Might have been better to isolate the clutch fluid from the rest of the transmission. The one item that for SURE wears and releases particulate matter is the clutch, throughout the life of the car. No matter what you do, clutches gonna clutch...Treating the circulating oil like a slushbox maybe a bad idea?
I know some people say they "pampered" their cars during break-in and still had issues with solenoids too, but I would be willing to bet there might have been a few "white lies" there. It's a performance sports car. People didn't buy it to drive it like a granny.
Problem is this means you need another pump and coolant loop, unless you could use some sort of internal heat exchanger.
I haven't seen a single "technical document" that discuss what exact material is fouling these valve bodies. GM is keeping us in the dark.
Melting Slicks
Joined: May 2021
Posts: 2,562
Likes: 1,579
But how does the clutch material get around the filters and to the valves? Is the filtration design inadequate and allowing unfiltered fluid to the valves? Filters bypassing prematurely? Filter media allowing too much contamination through? And keep in mind that slushboxes also have clutches.
Be careful, but if you watch the "Precision Transmission" channel on youtube, you might learn all the nuances of every auto transmission ever made.
Difference is in slush box you have a lot more surface area / clutch area, and the fluid flow may be different where 100% is filtered before returning to the valve body. Those internal clutch plates are also downstream of the torque converter.
I would be willing to bet the clutch pack in the DCT works harder and I am not sure about how the fluid flows. They do have TWO filters though. One in the pan and one external cannister filter.
Last edited by dohabandit; Apr 27, 2023 at 05:07 PM.
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Drifting
Joined: Feb 2023
Posts: 1,363
Likes: 1,129
Melting Slicks
Joined: May 2021
Posts: 2,562
Likes: 1,579
https://go4trans.com/technical-trans...-transmission/
The "downsides" listed in the above article appear to sound familiar.
https://www.planet-9.com/threads/diy...l-mode.237865/
A view of the clutch cooler, and gear cooler on the PDK.
To be honest, I think combining the two into one oil bath was a bad idea. Maybe done due to cost?
Or was it done to avoid a patent infringement? Who knows...
The "downsides" listed in the above article appear to sound familiar.
https://www.planet-9.com/threads/diy...l-mode.237865/
A view of the clutch cooler, and gear cooler on the PDK.
To be honest, I think combining the two into one oil bath was a bad idea. Maybe done due to cost?
Or was it done to avoid a patent infringement? Who knows...
Drifting
Joined: Feb 2023
Posts: 1,363
Likes: 1,129
https://go4trans.com/technical-trans...-transmission/
The "downsides" listed in the above article appear to sound familiar.
https://www.planet-9.com/threads/diy...l-mode.237865/
A view of the clutch cooler, and gear cooler on the PDK.
To be honest, I think combining the two into one oil bath was a bad idea. Maybe done due to cost?
Or was it done to avoid a patent infringement? Who knows...
The "downsides" listed in the above article appear to sound familiar.
https://www.planet-9.com/threads/diy...l-mode.237865/
A view of the clutch cooler, and gear cooler on the PDK.
To be honest, I think combining the two into one oil bath was a bad idea. Maybe done due to cost?
Or was it done to avoid a patent infringement? Who knows...
Drifting
Joined: Feb 2023
Posts: 1,363
Likes: 1,129
That’s how I look at it. It certainly seems reasonable to at least change the external filter every engine oil change. It’s simple enough, you won’t hurt anything and it could help avoid a large maintenance issue.
Racer
Joined: May 2022
Posts: 472
Likes: 238
"Keeping good oil in this system is critical. Poor oil will degrade valve body operation, wear the valve body bores and seals, and degrade clutch engagement. If the valve body isn’t operating correctly, everything downstream will deteriorate. Also the fluid is full of additives such as anti-shudder compounds that are essential to smooth operation."
Drifting
Joined: Feb 2023
Posts: 1,363
Likes: 1,129
And I would change the fluids and filter/ external filter before the recommended 7500 miles. How much sooner depends on how your car is used.
I would rather spend a relatively small amount up front to decrease the odds of having a much more expensive issue later on.
I would rather spend a relatively small amount up front to decrease the odds of having a much more expensive issue later on.
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Sucks that you are having problems with the transmission - especially since you supposedly had the problem fixed 7K miles ago. Hopefully with this repair the problem will not happen again, but if it does, and you decide to go for a different car, perrhaps a Caddy Blackwing would be a good choice.
Melting Slicks
Joined: May 2021
Posts: 2,562
Likes: 1,579
If tracking it is a requirement to replace all fluid after X track hours (24 right?). I think it might be warranted to replace the pan filter too. When I do that, I will likely replace the pan with a Dodson pan cover.
