'04 F-350 6.0.. strange squealing sound (long post sorry)

Ok, first, I'm sorry about the long post, but I want to make sure I give you all the details as best I can, so that maybe someone can tell me if I'm heading in the right direction with my thinking on this.

Let's start with the truck itself first. 2004 Ford F-350 Super Duty Lariat Crew Cab. 8cyl. 6.0 Diesel. Automatic transmission. 4x4. 62k miles.

I bought the truck used 2 months ago. About two weeks ago it started making an awful squealing sound. Its very strange in that its very intermittent. It seemed to do it a little more when turning left at first, but I also noticed it when I turned left and sometimes, though rarely, when I'm going straight. Nothing that I can see affects it. It doesn't speed up or change pitch if I speed up or slow down. If I come to a complete stop, so does the noise. It may or may not resume again when I begin to roll from a stop. It does it when the truck is hot, when its cold, if its dry or wet, with a load and without. And as I said, it comes and goes, it might do it for a second and quit, then not do it again for a week. It might squeal for miles, quit and then do it on and off for the next 3 days then quit for another few days.

Also the noise has no effect on the steering or power of the truck. It doesn't pull and it doesn't turn sluggish.

At first I thought it might be a sticky caliper so I had a friend drive slowly while I stood on the running board and listened. I tracked the sound to the right front wheel well area. I've had calipers go before, and this sound didn't seem quite right.

I got to thinking about it more and it seemed more likely to be a dry bearing, at least thats what it sure sounded like. So off to the dealer we went.

And what a nightmare that was. I understand its a used truck and was expecting some kind or repair work in the first six months. I also understand that intermittent sounds can be hard to track down. I don't expect rude service. But thats neither here or there.

Long and short of it is, they had it four days couldn't hear a sound, I figured since I was paying 55$ just for them to look at it anyway, I might as well get an oil change and have all the filters changed while it was there. So I told them that. They called me the next morning and said that when they brought it down off the lift, they heard the noise and that it was a bad hub and bearing assembly.

Ok, so I told them to fix it. They ordered the part and I got it back 2 days later. Along with an almost 1200$ bill. No biggie.. the bigger the vehicle, the bigger the repair.

Two days later the air conditioner vacum pump goes out. No air except through the defrost vents.

Fast forward to last thursday. I'm driving it, its been fine since I got it back from the dealer... untill thursday when the squealing comes back. Same noise, same side. I call the dealer, they say bring it in monday. So I parked it all weekend and took it in on monday morning.

It squealed almost the whole way there. It was squealing when I drove it into the service bay. The first repair was warrentied, so, no biggie, right?

Wrong. This time they had it 3 days, still couldn't track it down and told me to bring it back if it did it again. I don'tget it. That squealing is LOUD. They all heard it, but they tell me they can't verify it on a road test, and since its a sealed bearing, a visual inspection doesn't tell them anything. Well thats a big help. What happens if a bearing blows when I'm hauling a 20 ft trailer?.... I don't even wanna think about it.

So I got my truck back today, its not making any noises at the moment. Runs and drives fine, so I go get the ac pump and fix that. The air is working now at least.

But I'm kind of afraid to drive my truck. That noise is horrible, it sounds as it the whole right front end is trying to tear its self apart!

At any rate, after reading everything here... I'm thinking maybe its the needle bearings, or perhaps the center joint or u joints, though it seems to me if it was the joints the sound should change as the speed changes.

Any suggestions?

P.S Did I mention I had to call down to the dealer every few days to find out what was up? I don't understand why my trucks status was treated as a matter of national security!