I was getting on the fwy this morning on semi circle onramp with power on and noticed a faint-but-still-noticeable whooshing/hissing (sorry can't think of a better description) sound coming from the rear of the truck. Once straightened out, the sound went away. Windows were up. I need to try this with them down . . .

Anyway, could this be shocks, antilock, differential, maybe tires? It is really hot here today (95 deg). Don't know if that could be a factor.

Thoughts?