The hubs aren't going to matter. It's going to be the TC itself. Thoughts are that its actually stuck in 4wd. Have someone idle the truck while you watch the front driveshaft to see if it's turning. Also you could try going from 2wd to 4hi to 4 low then all the way back again going into drive and reverse once between each switch of the knob to make sure that it actually does change. Only after exhausting every option mechanically would I start to think it's electrical.