2007 Dodge Caravan high pitch whine

I purchased the vehicle new. At 20000 kilometers on my trip to Florida after prolonged driving I heard a high whine when stopping for fuel. After fueling and restarting the car it disappeared. The dealer in Florida could not helpme because I could not reproduce the noise. At 40000 the noise returned but still only after prolonged highway speed travel. The dealer where I purchased the vehicle could not help because the noise was not there. The noise sounded as if it came from the power steering pump. Chrysler told them to overfill the reservoir. This seemed to help temporarily. The noise returned as before so at 59000 I brought it in to the dealer and he wrote a letter that would extend the warranty. At 95000k The noise could now be heard and the dealer changed the power steering pump. This did not fix the problem. I returned to the dealer who said that this was a normal sound from the torque converterand would have to live with it. This certainly cannot be. I asked another mechanic and he thinks it is the belt tensioner. It makes sense to me because the noise comes from that area of the engine compartment. I certainly cannot live with this sound or even sell my vehicle. I contaacted Chrysler only to be told that this is normal. I again think this cannot be. Help if you can.