honistly everything anyone has to offer is going to be a shot in the dark. cant realy diagnose worth crap without seeing the vehicle. IMO, if its not an exhaust leak, or an air leak around a door, then its probably tire/hub noise. i say that because thats usually the most common. but "thats the way it is... until it isnt... then it wont be." so try this:
go on a nice strait road, swerve smoothly left and right. does the noise change when going left and back to right?
if so then probably a tire/hub noise
rotate your tires front to back and see if the noise follows.
if it does then its tires for sure.
while your vehicle is in the air, check hubs for play to determine/rule out hubs.
http://www.aleromod.com/forums/showt...&highlight=abs <-- briefly touches on how to check wheel beings.
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go 55mph (or where ever your car makes most noise). put the car in neutral and let the engine idle. noise change?
if it does then its engine/trans related
if this is the case get back up to 55mph. put the trans in "3" instead of "D"
maintain 55. did the noise change?