I've got a 2006 Yukon XL, 5.3L/4L60E, 65K miles. Yesterday on the highway it suddenly shot the revs up. I was able to get off the road and drive it slowly home. It will shift into 1st and 2nd fine (as well as reverse), but won't shift up to 3rd. It acts like it's trying to shift to 3rd, but it's like 3rd is missing or slipping - the engine revs, but no acceleration (i.e. it doesn't act like it's stuck in 2nd). I was hoping it was just a bad solenoid, but after some reading here on the forum, now I'm not so sure. I also took it to O'Reiley to have them check the codes, and they said there was just one for an EVAP leak - none for the solenoids. I was going to go ahead and try replacing the solenoids anyway and see if that fixed it, but didn't want to waste $100 in parts/oil if that's clearly not what the problem is. Really hoping to not have to replace/rebuild the tranny (just got the truck less than 2 months ago 
