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Wanted to relay a few issues I've been having with my C8.
1. I'm seeing some odd and scary behavior in response to flooring the throttle while cruising along in high gear. Normally I am in tour mode when I'm just driving around, occasionally sport, but since I'm normally in tour mode I can't say for certain whether it's happened in sport. But basically, it has happened both in lower-speed cruising (around 35-45 mph) and at highway speeds (60-70 mph): I'll be driving along in a high gear, nail the throttle, and the vehicle goes into a much lower gear, and then either exhibits rev-limiter type behavior (vehicle is not picking up speed, just parked at some midrange RPM level as though it's hitting rev limiter) or hesitates at a given RPM for a moment, bucks/surges, and finally accelerates as desired.
But it does not happen every time, it is sporadic. Last weekend I had it happen once while on the highway, tried again a few more times afterwards, same results, then when I exited and tried at lower speed it repeated a few more times. But the other day while trying to duplicate it on video, I had the exact opposite happen: it took a number of attempts to *get* it to happen. And then, in the most-recent (first) video, it did it mildly on first attempt, and then much more severely on the second attempt, which is shown in first video below.
Here are four videos of it doing it to varying degrees:
This is the latest video from the other day (turned on overlays this time, watch what revs do when this happen, foot is NOT taken off of gas during that time, it is pedal to the metal). Throttle is floored at 0:04 into the video and it downshifts immediately, but look at tach and what happens from then until just before 0:07 when it actually starts moving: https://vimeo.com/492686659
And here are three other videos of it doing it, with varying pauses from time it downshifts into lower gear in response to full throttle and beginning to actually accelerate. I do not release throttle from the floor until a second or so after it starts accelerating as it should. https://vimeo.com/491275807
Second issue is a whine from back end. Became noticeable around 700 miles or so and has worsened (1700 miles as of now). This occurs either under very light acceleration or light-throttle steady speed, and range seems to be increasing (was 37-50 mph, now it's extended out to up to 55 mph). Pitch of whine increases with vehicle speed. It is independent of gear. It stops in response to additional throttle pressure or throttle release. It stops if clutch is engaged (pulling back both paddles simultaneously). Below 37 or so mph or above 55 it is not present. Dealer filed TAC with Chevrolet, but they stated it was a slight whine: it is not slight, it is loud and can be heard over the radio at its peak (45 mph). Chevrolet in response to TAC stated this is "normal", but I've owned a number of performance vehicles, and it certainly wasn't present in any of them.
Wondering if anyone else is experiencing either of these issues?
Thanks in advance!
My guess is that something is wrong with your transmission. All of the shifting is supposed to happen in 100 ms. Your video shows that when it downshifts to 3rd it limits the rpm to 3500 rpm for a lot longer than 100 ms. It's almost like it thinks it's doing a launch. Take it to the dealer and let us know what they say.
That really sucks- so sorry you and others have to go through all these never ending problems. If it is not software glitches of every kind, it is cheap parts, failures in every area, fit and finish issues, NO true quality control - and poor production standards at Bowling Green where the workforce has no pride in their work.. This car should have never been released before they sorted out all the never ending issues - it is turning out t be GM's very own "Yugo". I think when I get mine I am going to sell it and make some cash on it and never look back.
Unless one lives walking distance to the dealer, returning it for repairs that take more than a couple cups of coffee in their waiting room can be a big inconvenience. Many will have to take time off work or change long held plans for the day. I, for one, will have to Uber it 25 miles home, and then Uber it again when it';s repaired. If my car requires repairs of items that are chronically in need of repairs in other cars, GMC will get a bill for my time and disbursements. They won't willingly pay it at the outset, but at some point they will have an attitude adjustment if there are too many of us.
Can’t help but think these problems sound like solenoids inside the DCT. Just like the first years of the GTR. Yes it shouldn’t happen and hopefully we’ll find out exactly what’s going on and hope GM is up front and on top of it. Hard to tell the actually numbers of issues based on so many variables. The first year is always something. It’s always been a long joke but so true. It shouldn’t happen but it does.
That really sucks- so sorry you and others have to go through all these never ending problems. If it is not software glitches of every kind, it is cheap parts, failures in every area, fit and finish issuesvery fe, NO true quality control - and poor production standards at Bowling Green where the workforce has no pride in their work.. This car should have never been released before they sorted out all the never ending issues - it is turning out t be GM's very own "Yugo". I think when I get mine I am going to sell it and make some cash on it and never look back.
Who did you order your car from and what are the specs? What is the ETA?
There seem to be very few problems for a car that was re-designed from the ground up and I'm sure the 21's will be even better: - New motor - New suspension - New transmission - New cooling system - New electronics - New lubrication system - New tires
Only people with problems post about their concerns. Many thousand cars are problem free.
I have 4,500 problem-free miles on my 2020 3LT/Sebring Orange/Cool Grey/Z51/Mag Ride/Lift/Carbon Flash/Silver Cover/Engine Appearance.
Unless one lives walking distance to the dealer, returning it for repairs that take more than a couple cups of coffee in their waiting room can be a big inconvenience. Many will have to take time off work or change long held plans for the day. I, for one, will have to Uber it 25 miles home, and then Uber it again when it';s repaired. If my car requires repairs of items that are chronically in need of repairs in other cars, GMC will get a bill for my time and disbursements. They won't willingly pay it at the outset, but at some point they will have an attitude adjustment if there are too many of us.
My experience at my local Chevy dealer is I'm either given a loaner or a ride home.
New disclosure: Was told that the C8 DCT requires a new $200+ filter at 7500 miles !!!! No mention of this in the owners manual. True ???Not sure if I was treated honestly
New disclosure: Was told that the C8 DCT requires a new $200+ filter at 7500 miles !!!! No mention of this in the owners manual. True ???Not sure if I was treated honestly
This service is required at 7500 miles. It’s supposed to be from my understanding the dealers responsibility for this first free service with oil change at 7500. It does seem like I’ve come across a lot of owners that are getting had on this one.
Last edited by NoMatter; Dec 21, 2020 at 07:38 PM.
These DCT filters do cost around $150. Seen one for $130 on eBay. Not sure how I feel about that yet. It look the same. Doesn’t surprise me the dealer charges $200. But not when the first service is post to be free of charge.
Like my GTR I had I’m hoping Dodson the company that is currently working on the C8 DCT with Cicio performance will come out with a lifetime filter for the C8 DCT. They were roughly $185.
Last edited by NoMatter; Dec 21, 2020 at 07:57 PM.
For whatever reason the GPS couldn't acquire the signal yesterday. The map was just black with the Arrow in the middle of the screen. The GPS "circle with slash" icon was flashing. I drove it for about 5 minutes and nothing changed. I shut the car off for about 10 minutes and it came back. All the other functions of the info system worked properly. Only the map was black.
I have no idea why. But, at least it works. It worked fine today.
Last edited by Sin City; Dec 21, 2020 at 10:52 PM.
Back in the late 60's and all through the 70's I struggled with electrical issues on MGA's, MGB's, a MGC, Midgets, TR4's, TR6's, Jaguar E Types and sedans, a festering old Bentley, a TR7, a TR8, a Rover sedan, a Jensen Interceptor and a 1/2 share in a Lotus Europa. ...oh I forgot a couple mid 60's British Army surplus Land Rovers.
What you are telling me indicates the C8 has Lucas parts, the prince of darkness !
"The transmission filter change is not included in the free maintenance, however some dealers have special offers for Corvette customers. Ultimately, we would recommend reaching out to your dealer to confirm what their pricing would be for this service."
"The transmission filter change is not included in the free maintenance, however some dealers have special offers for Corvette customers. Ultimately, we would recommend reaching out to your dealer to confirm what their pricing would be for this service."
Anyone know if one can change it out at home ?
That's Bull shXX. The filter is covered on the DCT and the engine oil change is free, all have to be done on or before 7500 miles and within 1 year,
