Towed my TT home from the campground this morning and had a whistling sound from the rear the entire drive home (about 120 miles in the mountains). Put the rear window up you couldn't hear it, rear window down you could hear it. It was the same sound no matter the speed and would only go away at a full stop. Engine and tranny temp were normal. As soon as I got home and unhooked the TT I drove it around the block and it was still making the noise. Unloaded all of our stuff and got some lunch then went to the dealer. Of course it didn't make it anymore after sitting for an hour. Service guy said all they could do is put it on the rack and check everything out.Sorry so long, but I wanted to present as many facts as poosible. Anybody got any idea what could be making a whistling sound? Read diff vent?