I'm new to this. I have a '02 gmc cc 4x4 dmax/alli. (Banks six gun w/ speed loader) 63,000 miles . When driving normal it shifts fine:) . The problem occurs when getting into the pedal (The shift pattern gets weird), First seems fine, shifts quickly through 2nd, and in 3rd revs up til I let off pedal and then it will engage:( . 4th and 5th seem fine. I bought truck second hand 2 weeks ago, I believe trans is stock :help: Also, what is an NBSU or what ever it is people keep having to replace?

Check the fluid in the transfercase. Sounds funny, but I had one about a month ago, would go to shift into 3rd and not go anywhere, till you backed off or came to a stop. Would even put the trans in limp mode if you held it there doing it. Strangest thing, so drive it some more, always 3rd gear, till finally it did it once in another gear, then got bad enough that it would seem like it popped out of gear. All this while watching shift selonoids and such trying to figure out what was going on. Finally it just was horrible, something had to be wrong with the trans. Went to pull out the transfercase, no more than a few drops of fluid in the transfercase. What was happening, the transfercase was being dissengaged by the worn shift fork. Never made any noise, other than a metal on metal noise when it would pop out and make you think the trans wasnt engaged. Just a thought.

thanks for the info Cobra, I'll see if that might be the problem