maryarg
As somebody previously told to you, the best thing you can do if help is needed urgent on that, is to share a drawing/outline/photo of the gearbox where those terms appear. And that's it.
"Tuerca de registro" = "Adjusting screw locknut" (I fully agree if no picture or further explanation is available)
"Zafe" It sounds like Argentinian Mechanics' Slang. Anyway my answer is as follows:
"Zafe de protección" = "Transmission Overload Protection". It is sometimes adjusted by means of a spring.
You can check the last part of my answer at
http://www.imet.com.ar/ where the following is written with the photo that appears below these lines.
c) Zafe : Protección de la transmisión (cadenas, caja de velocidades, ejes, distribuidores - dosificadores, etc.) ante sobrecargas. Fuerza del resorte regulable.
Source:
http://www.imet.com.ar/
Saludos a todos and Hope it helps
