WWIXMR

I have always loved watching rally all my life. But there is one question I always had in the back of my mind that I never bothered asking someone about.
I searched Google but get a bunch of results having to do with mechanical issues lol.

Anyway, where does the whining in a rally car come from? At first I was thinking, maybe it has something to do with the transmission. But then I thought, maybe it is the differential? I mean, our Evos make a whine(if your stock and can hear it lol) on the lower gears, but it is kinda faint.
Example:

http://www.youtube.com/watch?v=e0wcB...ture=quicklist
&
http://www.youtube.com/watch?v=ParmMRS8qp0

Kracka

iTrader: (49)

Straight cut gears.