SM3xx/SM420 helical gears.

[Crashbox]

Howdy-

I've been trying to find information on the helical gear cut angle for old Chevrolet SM318/326/330 three-speed and the SM420 four-speed transmissions. I cannot find this info anywhere, but someone must have it for cutting replacement gears for the aforementioned transmissions. If anyone does have this info and would like to share it, it would be greatly appreciated. It has really piqued my curiosity of late.

Thank you very much in advance.

 

[Crashbox]

The reason behind this, is that the whine these transmissions made was rather loud but also pleasant IMO, and I believe it was directly related to the helix angle on second, third and fourth gears (granny was a spur). I've also been pondering the thought of cutting/heat treating my own gears, perhaps as a business when I retire in the not-so-distant future... a niche market if you will.

 

[Crashbox]

Anyone?

Exploded drawings would also be nice, especially of the SM420