Front end clunking and buzzing noise during extreme cold

[CoveShocker]

Been fairly cold here the past few days, yesterday was -26C/-15F and my truck sat at the office for a few hours in the morning and again in the afternoon. When I drove it home for lunch it started making a buzzing noise that sounded just like the mudflaps were caught in the tires, I stopped right away before I ripped off the mudflaps and walked around the truck...nothing, mudflaps weren't the problem. So I started driving again and same thing but add in some fierce clunking noises from the front end...exact same clunk that the 4x4 makes when it shifts in hard, did about 3 or 4 quick clunks and then it all stopped after 2 minute of driving. On the drive home for supper, same thing happened. This morning, again it's pretty cold -26C/-15F, exact same thing and then it stops after a minute or two.
The other weird cold weather noise I've heard is a popping noise coming from behind me, sounds like the frame is shifting like a huge load is in the back but the truck is empty, happens going up or down logging roads...doesn't happen that much but it's a loud pop when it does occur.

[CoveShocker]

Got it back from the dealer this afternoon after letting the truck soak in the cold for most of the day. Turns out the thumping and clunking from the front end are the hubs spontaneously trying to lock in. Apparently Ford is working on a TSB to deal with the hubs trying to lock in when the temps are below -17C. The temporary solution for now: when the temps are below -12C, I'm supposed to manually lock in the hubs so they don't self destruct when it gets colder.

[grooveman]

Other noises aside, is it normal to get a pretty loud "clunk" when the 4wd is engaged during extreme cold weather? I do hear that with mine, but it seems to be locking in and running fine after 4wd is engaged.

[CoveShocker]

I'm told it's normal to have that "clunk" under normal circumstances. In my work I use 4x4 at least once or twice a day from Nov to April....so I sure hope it's normal otherwise it's going to have a short life.