Rubbing noise

I have a 2001 XJ and it seems everytime I give it gas to turn there is a weird rubbing almost grinding noise. It sounds like it's coming from the back tire. I can feel it in the steering wheel and in the seat. I've brought it to the Jeep dealer a couple times and they keep saying nothing is wrong with it. They actually replaced one of the u joints and that didn't solve it. Also, it seems when I'm stuck in stop and go traffic my wheels make a high pitch squeeking sound when they roll once the car is warmed up. And once I apply the brakes the noise stops. Except when coming to a full stop at a decent speed then the brakes make a squeeking suond. Which is another thing I had it in the dealer for. And of course they told me nothing is wrong. If anybody has any insight I'd greatly appreciate it. Thank you.