I agree with Donf - that's pure music! But, it's not from square-cut gears, as all the gears in the 3 and 4 speed trannys from that era had helical gears. Here' a picture of your unit:
http://chevy.tocmp.com/shop/1941/41csm208.htm

It looks like a Muncie SM420 but they didn't come out until '47 and were used for many years after that.

I don't know what yours was called, maybe someone else with knowledge of the older transmissions will come by later. It