I'd like to start off by saying that we recenly got a ton of snow and ice here in Ohio and my truck(2004 FX4) performed perfectly. I was always unsure if my 4x4 was working because I could not feel or hear it engage but with the snow and ice there was not question - it was awesome! This morning I left to go hunting and halfway to my destination I was coming to a stop and heard a rumbling noise (sounded like mud tires on asphalt). Thinking that it was snow or ice on my tires I did not pay too much attention.... except everytime I would slow down to stop I would hear it again. When I got to my hunting spot I needed to engage 4x4 and instantly the sound stopped. I did this a few times and each time I put it in 4x4 the sound stopped (I only turned in on in snow or ice). After hunting I got in my truck and drove down the road and there was no noise what-so-ever..... all the way home. Does anyone have any idea as to what this sound was - I'll call the dealer tomorrow morning and run it past them but I figured that I'd ask the experts first.

Thank you!

 

Are you sure it wasn't the ABS kicking in when you would stop? The ABS makes the noise you describe, and since you said it only happened when stopping this was my first guess.

 

Snow on your front axles.