Why is hot air blowing from vents n it not on n when itson? Also my 4x4 ddoesnt come on without manully locking hubs.

Vacuum leak

If it’s hot air like the heat is on then check the blend door behind the glove box or if it’s not blowing cold then a A/C issue it’s unclear to what the problem really is I have the almost same truck and I have experience every issue I think you can have. Good luck.