Well, I got the truck back and again no improvement. I am pretty much done...I've been dealing with this since the 14kmile mark. I talked to the tech and he doesn't understand as well and after changing the fluid twice and inspecting everything within the drivetrain, basically has no answer and thinks it's all due to he fuel mgmt system, which we ruled out months ago as it is still bad in trailer mode and L9. They are now saying the fuel mgmt system never really shuts off 100%.
Two weeks ago the slipping 5-10 times the acceptable level is now considered "normal" by my dealer and GM engineers. I will most likely be trading truck within the next two weeks and GM will have to continue to deal with it as anyone that drives it for more than 10min will realize something is not right.
There is a reason the transmission was destroyed after 25-30k miles and I know the new tranny is on a similar path as bad as it is shuddering and slipping.
No improvement after the following:
Software updates
New motor mounts
New torque converter
New transmission
New rear R&P
New fluids (multiple times)