WTF Could this sound be???

Hey guys, I went out to the desert to do a little bit of wheelin with my lady today and when we got back the pavement my truck had this weird squeeling sound coming from the rear end. At first I thought it was sand or some rocks that got caught in my rear drum brakes, but the sound isn't all the time...its just when I throttle up...like rev it up when I 'm driving...not while i'm in neutral. I checked the spare tire...the muffler and all that stuff...i'm starting to think its my drive shaft. Any thoughts?? Oh and it's loud! But its only when I goose it to accelerate...Its weird

Thanks for any input guys

 

Thats what I was thinkin...I'm gonna stop by the self serve was tomorrow and spray the hell outta it and see if that helps

I've narrowed it down so...Its not the brake, the spare tire isn't loose and my muffler supports are solid...its either my rear diff or the drive shaft I think...but like I said I'm not sure

All I know is that it sounds $$$$$$$$$$$$$$$$$$$$$$$$$$$

 

or...wheel bearings...bearings plus sand equals hell

 

I say hit the whole driveline with some high pressure water, then grease up everything with a zerk afterward....see if that doesn't kill the problem.

 

Thanks for the ideas guys!

I took it through the wash today and it did get better so I think it's some rogue sand in there...