That is very good news. Thank you for the information! Much appreciated. 👍🏻

Summer 2020 Vibes
 

Just picked up a used 2018 2SS automatic with 19k miles (got a great deal) but unfortunately didn't test drive the car long enough to feel the infamous shudder. Was driving it home on the highway when I felt it. Man it was a bad feeling in the pit of my stomach

Good news is my car still has 2 years of power train warranty and I took it to my local dealer and they did the trans fluid flush and replace. Bulletin 18-na-355. Since then I've put around 250 miles on the car and have not experienced any vibration, shudder, or rumble strip feeling. Very very rare but I get a little trans slip while accelerating hard and the car downshifts - this could be something else and it doesn't happen enough for me to be concerned. Will update if the shudder ever returns. May look into extending my warranty in case I ever need a new torque converter.

I guess that's one way to go. I don't know how much those cost, so can't really comment.

My thinking is that if my 8-speed starts acting up after my powertrain warranty is over, I will find a good transmission shop favored by enthusiasts and ask them to re-tune it. There have been enough posts on this site about people who have had excellent results doing that, and I don't think it is terribly expensive.

The dealership technicians are focused entirely on factory designed specifications, maintenance, and repairs. Their expertise does not extend into going beyond what GM says. The places that tune automatic transmissions know how to do these things. They can alter the tables that control how the transmission behaves.

Anyway, that's my plan.

My 2018 2.0T A8 did this just after 2000 miles so I don't but the GM story the oil is the problem. My post is under ACEPA. I purchased my car in China while at the same time my friend bought her Camaro the same day and never had this problem. Still trying to resolve in a foreign land. I put 400KM on the car before I could stop and flush and replace the oil. One thing I noticed is the transmission oil I removed was more like red oil. The new special mobil synthetic oils looks more like red water than oil.

Frustrating I feel your pain with this issue I thought my 2018 2.0T was amazing the ride, the power, the looks and to be cruising at 50mph and low throttle and have the vibration start was truly heart breaking.

I would definitely look at your drive shaft couplers.. or your carrier bearing..or mounts and alignment on everything before you go after the transmission

A8 transmission problems
 

There is a current class action lawsuit against GM for transmission problems on the A8 transmission. Call the law office of. Cohen Milstein at (561) 515-1400.