912E/923 Transmission, I need some insight.... Options

[Britain Smith]

Can anyone provide me with some random bits of information about the 912E transmission?

As you all know, am building a fairly powerful type-4 engine and I was headed down the path of mating it to a 915 transmission. I could either (A) use a conversion flywheel from Kennedy and machine it to match my dowel-pinned crank, or ((IMG:style_emoticons/default/cool.gif) use a 923 transmission from a 912E which has a type-4 mainshaft and would allow me to keep the dowel-pined, lightened flywheel that I already have.

I know that the 923 tranny is a mag case with a 7:31 R&P which has it's own set of issues, but I need some additional information to sway me either way.

I am also interested in some further explaination of the gearing. The 912E gearset looks like the following:

1976 (5-Spd) 11:35 11:33 23:29 26:25 29:21 7:31

Is there any reason why the first and second gears are so close in ratio to each other? I plugged this into my calculator and found that the 1-2 shift is ridiculously short...this can't be right. The 72-73 & 74 915's gearing looks like this:

1972-73 915 11:35 18:33 23:29 26:25 29:22 7:31
(5-Speed)

1974 915/06 11:35 18:33 23:29 27:25 29:21 7:31
(5-Speed)

Do you think that a type-4 motor would be better off with the 912E gearing or the normal 915? Anyone? Jake...I know you have done a fair bit or research into this, any thoughts?

-Britain

[bondo]

I don't just mean in terms of the shift points being too close, but also physical meshing of the teeth. The centerlines of the 11:33 gears would have to be closer together than the 11:35 gears.. but they all have to fit on the same two shafts. If you scaled them up, I don't think they would mesh properly. I'm not a transmission designer, but I have rebuilt a few and the 11:33 just doesn't make sense. It's gotta be incorrect data. Someone here must have a 912E they can push in 2nd gear and count distributor and wheel turns (IMG:style_emoticons/default/smile.gif)