alot of new cars are coming with helical cut reverse gears now. people are getting very picky and didnt like the reverse whine.

and, if you were to put a straight cut gear against a helical cut gear that were made of hte exact same material against each other, the helical gear is stronger, and has much better lubrication properties. the gears in race transmissions are built out of different kinds of alloys, which are usually kept secret.