Ever since the first day I had my truck, when I shift into Reverse (it's an auto) there is a hissing noise. Sounds like a vacuum hiss.

There's never been a problem, shifts fine, never lags into reverse, never threw a code and I've had the fluid changed at 25k and it still does it.

Any one know what it is?

 

Its a Ford. It will always make noises. I don't have a stereo right now and I hear all kinds of noises from everywhere when I drive.

 

HAHAHAHA.

I'm not worried about it, just curious as to what the hell it is.