Originally Posted by BDGreen
I have a 2016 GMC Sierra 1500 and have had tranny problems off & on since I bought it. It's been to the dealer twice & both times I was told they couldn't find anything. I took it to an independent tranny shop and told there's a problem with the torque converter on the GM 8 speed transmissions. They changed the fluid and it's been fine, but I'll have to have it done again before too much longer. I got a letter in the mail from an attorney stating there is a class action against GM over this issue. It might be worth it for you to look into that and see if your year model is in that.
mine hard shifted for a little while and had the fluid changed during a service and it stopped. Figured that fixed the issue. Now it went out completely and im picking it up tomorrow after the dealer had it for 6 weeks to replace it.