I have 2017 Sierra 6.2/8 speed NHT that developed "the shudders" at 25,000 miles. They changed the transmission fuid but no change. Torque converter was changed 2 weeks ago. Now it is incredibly smooth. There still occasional light clunks between 1-2 gear in parking lots, but I think most 8 speeds do that.
I read somewhere that when making the torque converter, the manufacturer was damaging an internal seal and fluid was not flowing properly and that the new torque converters have a different part #. I'm not sure if all of that is true, but I would hate to have to replace torque converters every 25-50,000.