Strange rubbing noise at 40 mph...? on 2004 Honda CR-V

I test drove a 2004 Honda CR-V (at a Honda dealership) and there was a strange rubbing noise every time I reached 40 mph, while both speeding up and slowing, as well as with and without my foot on the gas or brake. Sounded like it was coming from the rear. Any ideas what this could be???

Asked by for the 2004 Honda CR-V
Does it matter? I would run, not walk away from this car!! It could be a bad rear differential, bad rear bearings etc etc. the fact that this dealer is trying to sell a car with an obvious problem is a huge RED FLAG!! Shop some where else. I recommend using a place like Craigslist to find cars and then if you find one that you like, have a shop check it out.
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My CRV 2014 has rubbing noise every time I press the brake to stop. Dealer told me the pump is defected. Suggest you not to buy this car, I don't like it very much. Moreover, I heard CRV all-wheal-drive is not a real AWD.