Ive got a 99' F-350 dually with a powerstroke diesel and 6-speed. When you shift the **** on the dash into 4x4 it works fine. When you click it back to 2wd you can feel the transfer case shift out but the hubs stay locked in. you have to get out and play with the lockouts and wiggle the u joints on each side to finally get them unlocked. What could be the problem. Also, when you shift the **** into 4 low, there is no speed difference noticed at all, is it not shifting into low? if so what could be the problem here?

Thanks for the help