Hello! We had a shudder issue in summer 2018. Dealer flushed trans in July 2018 under warranty and it’s been fine until three weeks ago when it happened again. Somewhere, I read that in 2019 or so, GM changed to a newer transmission fluid. Does anyone know what Tech Bulletin covers this and what exactly the new trans fluid is? Also, if it was covered under the tech bulletin and warranty would it be covered now? Thanks!!!