break or transmission problem

[garycgui]

I just bought a new Giulietta two weeks ago, I found that when I hit the break, before complete stop, the car shakes a little bit and a sound came out from the engine part. I switch to manual mode, the car downshift to first gear right after the shake. I don't know if it's something wrong with the transmission or the break. Has anyone have the same problem?

Thank you.