When I'm in 4 high and I coast I can hear something from the front drive line. It's a soft whirring/grinding type noise.

If I'm accelerating there is no sound . Only when the driveline forces reverse and the engine starts to slow the truck do I hear something.

With my hubs locked but in 2wd I don't hear anything.

Is this something to be concerned about or is it regular noise?

We have had a brutal winter so I've been in 4x4 75% of the time.

 

I posted about this. I get a very similar noise, I believe, and am trying to figure it out.