I am getting a loud whirring/grinding sound (sounds like tire tread rubbing on plastic but its not) after hard acceleration or cruising at highway speed (70 mph). It immediately stops when the 4x4 is engaged and the sound is only present when coasting. Also, air starts coming through the vents when going up a hill. Are these problems related? Possibly a vacuum issue? It sounds like the 4x4 or transfer case is partially engaging and making a HORRIBLE SOUND! PLEASE HELP!
I had a similar problem in an unrelated car (2002 Subaru WRX) After my car was towed for parking in an off limits area. Whwn I got my car back, I tried to burn out, but being a awd car it just hooked up. When I finally let off it was making a horrible sound also. It sounded exactly like a baseball card in a bike spokes. It also only did it when I let off the gas, since under power the grinding was not being allowed. I tore my rear-end apart and found that I had broken one tooth on my pinion gear. Just thought that this case me be the same since the symptons sounded the same.