I have been working to get the noise level down in my truck. I replaced the weather stripping yesterday on the doors and the top. Wow! No more wind noise. Much better. But as a result, I'm hearing things I couldn't hear before. One of the things is noise from the rear differential which has a Detroit Locker in it. I've noticed that when you're on the highway and you back off the throttle just enough to get the rear end to coast, the differential makes some interesting noises (sounds a little like driving over textured pavement). I'm assuming that this is normal and due to the locker trying to decide what to do with both wheels coasting. Could someone confirm this?

 

Follow up: The noise from the rear differential while coasting was from not having enough pre-load on the carrier bearings. I pulled the carrier, reset the carrier bearings preload and the ring/pinion gear lash, and put in some fresh oil. It's nice and quiet now. Problem fixed.