I have a brand new Sonata SE 2.4 with the Automatic transmission and didn't notice this during the test drive. At around 40-50 MPH, when stepping on or releasing the throttle gently, it almost feels like their is a mild rumbling or shuddering in the transmission. Usually when stepping on or letting off the accelerator lightly but sometimes it will keep doing it if you gently hold the accelerator. I'm not noticing this at higher speeds. Seems like maybe the transmission is trying to stay in 5th or 6th at too slow of a speed. Anyone else notice this?