They did not do a flush, so no time wasted there.
For what it's worth, I am very pleased with the way that they are working to correct the issue. Not every car is perfect, there are a lot of systems that need to work well together and while it is a hassle to deal with the issues, the real measurement, at least for me is how the manufacturer works to correct the problems. It's hard to know if it's a quality issue from GM or one of the many vendors they rely on. But I can say that in my case they are eager to resolve it.

I hope that you have the same result Megahurtz.

I have been having the very same vibration problem from the A8. Turns out the dealership had to replace the torque converter! It took two days but the good news is that the warrantee covered it all plus a loaner. After getting it back on Thursday 12/29/16, it seems to better all better. I will put a few miles on it and see if the fix is permanent. I wonder if using the manual shift feature of the automatic trans has caused this converter problem? I have a friend with an AMG who said that using his paddle shifters cause a problem for him. I realize that a Merc is totally different than the Gen6 American muscle but just a question.

Took the car to the dealer this morning. Was easily able to recreate the problem. New torque converter is ordered. They will replace the converter, flush the system, and reflash the trans tune. No hassle at all. So far so good.

My 2017 SS is doing this and I have been scheduled to drop it off next thursday at the dealership for them to diagnose it and hopefully fix it shortly after...Does anyone have their TSB number? I would like to be able to tell the dealership so they will know exactly what to look for and how to look for it.

Got my 2017 SS back from the dealer. They did the triple fluid flush and filter change per the TSB, updated the TCM software, and reset the transmission learning. They asked me to drive it for 300 miles and report back. SO FAR it actually seems to be fixed. I noticed the TCM update keeps the car in 7th gear rather than 8th gear for a little bit higher speed before it shifts into 8th. They said if I have any issues after this they would just change out the converter. Being that my car is a 2017 Fifty and built in September 2016 it already had the newest version of the converter.

I was reading that the TCM programming has to be adjusted for different TC's and solenoids for it to work correctly. So perhaps it really is software related. Not sure of the purpose of the triple flush and filter swap though.

I had similar issues back in May, had my dealer reprogram the TCM and ECM, was a night and day difference, works great still.

Mine has done this for a while too, haven't brought it into the dealer yet. I can recreate it at will by being light on the throttle, just heavier than steady state cruise. Car does it every trip.

There's been three other worrisome issues I've had though, but each has only occurred once.
1. WOT shift from 3 to 4, in regular auto mode. It completely missed the shift and acted like the tires broke loose (e.g. traction control light on the dash blinking, torque mgmt full power reduction). Backed off the throttle, it upshifted to 8, drove normally.
2. Severely delayed 1-2 upshift. This one happened this morning, an uncharacteristically cold morning here in Houston (33F). I let the car warm up in the driveway to full operating temp before leaving, but the first shift took until 3,000 RPM'ish at just enough throttle angle to actually increase speed. Drove normally.
3. Harsh and delayed shift, can't remember which gear change, but was not @ WOT. Again, after the incident it drove fine.

ETA: Car has less than 4,000 miles.

you should take it to the dealer ASAP. It is my understanding you can cause damage to the torque converter, or shall i say excess wear, if you don't get it corrected.

Dealer replaced the TC and fluid with Mobil HP. I have driven the car about 100 miles and am happy to report no shudder! If the issue re-appears I will update.

300 miles after the triple flush, filter swap, and TCM update. Still no shudder. Hopefully it doesn't come back.

I wonder why some need a new Torque Converter and some don't for the same shudder issue?

I have the same issue where my car vibrates. It does it at 2500 RPM and sometimes at around 4500 RPM. Now my car is the 2.0T Turbo but this is the closest post I could find that was similar to my issue. Except for the 5th generation forums where they experience the same thing and had a fix which was to replace the torque converter and do a flush. That seemed to fix most of their issues and there was even a bulletin put out from GM I believe. I have a automatic as well. I was considering bringing in my car with all if this new information and requesting a bulletin check. I've brought in my car a hand full of times for them to tell me that it was normal. It was extremely aggrivating to hear that the dealer you bought your car from doesn't want to help your situation. Here is the website where the generation 5's experienced the same thing and found a fix: http://www.camaro5.com/forums/showthread.php?t=161698 Also here's a picture of a bulletin I found. Forgive me if I give any wrong information regarding the bulletin. I'm trying to find out the problem also without the most experience regarding this issue. It's post number 329 on this page:http://www.camaro5.com/forums/showth...161698&page=24

I'm also not sure if this fix would work for the turbo🤔

Welp, I guess I am also joining the shudder squad. I have less than 1200 miles on the vehicle and notice the same shudder/vibration as everyone else. I hope this is a simple and lasting fix, as I bought this car to replace my 335xi with its lasting issues. Only time will tell. I have scheduled my first oil change and for them to take a look at my issues this Friday.

How often does is shudder/vibrate for you guys that had the issue? I noticed what felt like "driving over rumble strips" one time about the same speeds but has yet to occur. I thought at the time it was the differential fluid being cold since I had just made a sharp turn and it was definitely cold out.