I have been trying to research this with no result. I have a 2005 1500HD 2wd 6.0 4l80e . after getting on the freeway and reaching at least 60MPH for 5 to 10 min my engine load and rpms will rise a little and the transmission will begin to shift hard and engine light comes on. I can turn off truck and start right back up and all is good or if I keep it under 60 it takes a lot longer to act up. On the back roads it has not messed up yet. All shifts are hard when it happens. I have checked the fluid looks good don't know how old it is. I don't have a tech 2 or a scanner that will test each part but wanted to see if their was a way to test each solenoid or the TCC with a multimeter or maybe someone has a option on what to do just don't want to do a fluid change and have to go back in I know it's probably an actual part that is bad.