As soon as I start to accelerate a bit (right after starting the engine) I can hear a sound that seems to be coming from the back. The only way I can explain the sound is that it sounds like some sort of Star Trek thingy engaging? I have a 2011 DC Sport. This happens every time I start the car and begin to drive (but only once). Can anyone help me with this? Newbie to Tacoma's so it's probably an easy answer but I've no clue.