I'd be pulling the cover off the pumpkin myself, ESPECIALLY if I had the factory LSD. Did y'all change the rear diff fluid at 30k like you were supposed to???

 

Just got the truck little over a month ago; took it to the dealer on Saturday and had the rear end serviced, fluids changed. Pulled the trailer on Sunday with no sound; dealer said the fluid had not have been changed and was the reason I was hearing the sound. I'll keep an eye on it........ I'll probably have the fluid changed again in about a month just to be on the safe side......

 

Please let us know how it works out for you

 

No problems; pulled the trailer to Cherokee, NC. Averaged about 12 mpg on the trip. Funny thing, once we unhooked the trailer the truck seems to be getting better gas milage, not sure about this one........ In Va Beach I was getting around 12-14 mpg and now it's stuck on 16.5 per gallon; maybe the work pulling the trailer cleaned out the pipes.....

 

It's wheel barrings cause I have the same problem and I had it looked at and found out that is my wheel barring in my front wheel

 

I would check the pinion bearing changes the angle on the axle when towing and under acceleration. Mine did the same thing about a month ago rebuild the entire rear axle.

 

Try driving around that speed and swerve left and then right. See if the sound changes or comes and goes. If it changes when you swerve then it could be a hub bearing going out. Just finally had to replace my driver side front a few months ago at 129k miles. Sounded fine until I went around a curve and then it would make the most horrific grinding sound during the curve.