I'm curious if datsun 4-speed tranny and 5-speed tranny are just the same but the fifth gear is forced by adding some gears. Anyone knows? And is there some sort of gear sets for datsun trannys anyways? And how could i calculate gear rations if i have to go with 4-speed but change the 3rd and 4th ratio so that they are bigger. Need knowledge :/
Here's a handy little gif to show that a 4 speed does not have a 4th gear. Power is simply transmitted straight through the mainshaft and out the back.
A 5 speed has an overdrive gear behind the reverse gear. The bottom counter shaft gear is larger than the one on the mainshaft. Thus the mainshaft turns faster than the engine. Even a 5 speed has no 4th 'gear'