Kia Sportage Forum : “Why dosn,t the 4x4 work when i put it in 4 wheel drive?It goes in gear but the f...”

Sounds like a problem with the auto locking hubs, or perhaps an electrical/vacuum problem.  I'd have this checked by a mechanic as there are a variety of possible issues here.

probably the hubs. they are crap. you can get replacement ones from warn which must be better than the Kia parts.