4WD does not completely disengage

[SeattleBlaze]

I have a factory '94 Explorer XLT. When I push the 4X4 button on the dash to turn off the 4WD the light goes off but when I drive it there is a loud sound like when you put playing cards in your bicycle spokes as a kid. It comes from the left front wheel and increases in frequency as the speed increases. This happened before I was able to get it to stop making this noise by doing a series of very sharp turns and then I hear a BANG in the front end that sounds like someone is hitting the suspension with a sledge hammer or the front axle is breaking. It is a super loud bang that I don't want to do again if I can help it. I forgot to say that the left front end drops about an inch when the bang happens and the bang only happens when I'm doing a sharp left turn.

 

[little x]

Your hubs are blown. Don't just replace the one on the left either. What's happening is the one on the right is engaging while going forward which (because of the opened diff) causes the left one to attempt to engage in reverse (even though the wheel is spinning forwards) causing one hell of a racket.