@Garycoral , I went out for a spin and got the grind/whine captured on video. Here are two videos I took on PDR. The first is longer and begins at a lower speed so you can see where it starts/how it sounds, and the second starts when it is already occurring.

This third one is one I captured illustrating issue I described at end of previous post. I don't drive in sport mode very often, normally in tour mode. However today I wanted to see if I could duplicate this in sport mode, and sure enough, on first attempt it did....but Brainiac here forgot to engage PDR, and of course the first three tries after this worked flawlessly (it is an issue that seems to come and go), but managed to duplicate it on the fourth PDR-on try. For me it happens when at a steady cruising speed, at city and highway speeds, cylinder deactivation not on to rule this out, stomp the gas and hold it. Here throttle is pegged from 0:19 to 0:24. It downshifts immediately, but then it first starts to accelerate, then hangs at about 3700 RPM for nearly two full seconds before it finally starts to get with it again.

 

I had driven it the evening before. I had no problem starting it this morning and have the GM Tender otw. I left the spring clip battery covers off for now. Maybe a fluke?

 

As with everything GM, they will find a way to cheap out on something.

 

I made a video today from the PDR but I can't upload it - What format does it need to be?

 

It’s probably too large to fit within the forum maximum upload size. Try a free sharing service like Vimeo.

 

I uploaded it to YouTube - Skip to the 4:22 mark... I don't think mine is as pronounced as yours but mine but I can sure hear it: https://wyoutube.com/watch?v=f_IUfmk5k9Yww.

 

@Garycoral , thanks for posting! Your link has a typo, I had to remove the w in front of youtube to get it to work. But I can definitely hear it, definitely a lot less pronounced than mine and I don’t hear the grinding elements of it. But mine definitely worsened over time; how many miles does yours have?

 

2000

 

Lol I’m 37 ahead of you. 🙂 Well, hopefully this is good for you as yours is much more subtle so doesn’t seem to be nearly as out of whack as mine is.

Although having said that, on mine it seems to be much more noticeable in higher ambient temperatures, and for sure where you are the ambient is quite a bit lower than here. 🙂 So definitely keep an eye on it once things thaw out.

 

Could it be the ring and pinion? Please do not take this the wrong way two things can make a difference make that sound if it is coming from there and one is not allowing the gears to mesh together long enough before too much torque is pushed through.

The other is not letting the diff get warm enough before putting too much torque through it. Only you guys who drove it know the answers. Unless either of you received one of the random test vehicles that plant QC employees drive for about 20 miles or so. Just trying to narrow down anyone getting on them before the break in.

Most important thing with the drivetrain is time and temp. Too much too quick leads to all kinds of funny sounds and vibrations.

 

Nah, I babied this thing through break in and well beyond that. I didn’t even give launch control a go until a few weeks ago, and that was two times just to see the what it was like. This is why it took so long for me to notice this crazy behavior when it’s floored: I really don’t floor it very often! I think I just got a defective unit, sux.

 

Mine was from day 1... I followed break-in by the book.

 

Improviz, it's easy to hear the roughness and gear noise in your first video. It's not subtle, and definitely sounds like most rear gear noise I've heard or experienced. The coarseness at the beginning is puzzling. Either way, GM service shouldn't be writing this off as normal. Nobody would want to listen to this noise. Hopefully, GM will step up and fix it.

 

So far I've reached out to the "customer service" rep who posted early in this thread, and she's been more than worthless. Basically zero input from her side other than to parrot that they're deferring to the dealers and that she'll get in touch with them. When I ask for any inputs from GM tech support, she keeps referring to the dealer as "our experts in the field" on an all-new car with which they've got little collective experience, as though poor GM techs know absolutely nothing about it. She refuses to put me in touch with nor forward my questions to GM tech support, and will not even give me her supervisor's contact info so that I can escalate. So clearly, her posting here in this thread was nothing more than window dressing to make it seem like they give a crap, which they clearly do not, at least not in my case.

I'll take it to the dealership again (which, for the record, is Classic Chevrolet of Grapevine, TX, supposedly one of the best in the area--I'd sure hate to see the worst), but they seem more interested in washing their hands of it than even opening the damn rear end up and scoping the diff as they should be (and would be, if they were the slightest bit interested in fixing it).

Extremely disillusioned about this experience. The sad thing is I really love the car, but my fears (and others' warnings) of GM customer service are smacking me across the face right about now.

 

Hey, you did what you could. Now drive it and let it implode. Then they'll be forced to deal with it.

 

If it were me I would confirm by email to Chev and the dealer you have sent them evidence of the problems, they refuse diagnose or repair, you intend to continue using the car and therefore will have no responsibility if there is a catastrophic failure of the car.

 

would the lemon law apply here?

 

My posting above was to ensure once your car takes its final "bow", you avoid the 'he said-she said' situation where someone tries to say you were told not to drive it, to schedule service, etc.

I believe each state has it's own lemon laws....google it.

 

One option (if possible) is to drive another C8 with a tech and then drive yours to note the differences.

 

Try selling it to the dealer for MSRP or MSRP plus a markup. If they think the car is perfectly okay than they will WANT TO resell it. Sorry to hear about your problem. In the 80's I had a 78 corvette and the Dealership could not/would not provide me with a lower radiator hose. They said GM did not sell them?