The 4x4 engages perfectly, hi and low.
When I go straight, its perfect.
Whenever I'm driving on 4x4 and turning, there's that weird "rumbling" or "heavy rubbing" sound, like if the front wheel was rubbing on the fender. But it's not!
If I turn and stop the truck while turning, the noise continues, even if I'm stopped and put in neutral.
The noise goes away when I drive straight again for a couple of feet/yards.
The problem seems to be worst when I go backwards. I think I can feel some resistance too, if I let off the gas, the truck will stop quickly.

advise?

 

Any truck will "resist" tight turning in 4x4, especially when not on extremely slick surfaces. Very very hard on them

Is it during "tight" turning or with ANY turn of the wheels?

 

Are you driving on the street in 4wd? Most 4wd's vehicles in 4wd will fell binding skipping tightness ect on turns. It is exaggerated more on pavement. 4wd is never to be engaged on dry pavement.

 

I know that on my truck i had a problem like that, except mines 2wd, it turned out to be the fan hitting/rubbing the shroud next to the coolant overflow, but it was a horrible noise when it was happening.

 

hum...no it does it on gravel, grass, mud, any terrain.
But why would the sound continue even after I stop?

 

Well like DeerKiller said check the fan or anything that moves with the engine. That would be one reason why it makes the sound when stopped.

 

thanks!