We just purchased a 2013 E250, we have about 500 miles on it. We hear today a whining type noise, like a fan powering up and then powering down. It seems to only happen when going between 15-40 mph, goes away when you stop or when you go past 40 mph. This van is equipped with an auxiliary transmission cooler. When we first heard it we thought that is what was making the noise since we were in traffic in about 90 degree heat. We didn't hear it on the interstate but when we got off our exit (after about a 300 mile drive) and was driving up our road (speed limit 35) we heard it, it went away as we were pulling into our driveway so we couldn't pinpoint it. While we were driving I got into the back of the van and listened over the fuel pump area to see if that was what was making the sound. It seems to be coming from the area right behind the seats to the engine area (kind of hard to pinpoint while driving, I can't run that fast). Has anyone experienced this or heard of this? If so please any and all thoughts would be appreciated before I put it on a lift at work or send it to a dealership.