Reverse gear whine has me curious...

Being this is my first Toyota, I've noticed a distinct whine when using reverse. Makes a "wind-up" kind of noise. Come to think of it, I've noticed this on a lot of Toyotas, old and new, which leads me to believe it's completely normal.

I'm not concerned by it, just curious: what causes it? Is it the way the gears are cut?

 

Never mind. Found the answer:


"The teeth on gears of mass market automobiles are not straight-cut, but are helically cut, in order to reduce gear whine. Reverse gear often is straight-cut, however, leading to a characteristic whine from many cars when reversing."

Excerpt taken from:
http://www.spiritus-temporis.com/manual-transmission/internals.html

 

The Tremec T-56 in my GTO has constant mesh synchronized reverse, I guess that's why you can't hear it. Why do you think Toyota (actually Aisin) uses straight cut gears for reverse? Cost savings?