bmoses

Great info guys, thank you. It seems to me that replacing these gears is equivalent to changing rear end gear ratios in the driveline, yes? I say this because this ratio is AFTER the reduction gears on the input shaft and countershaft, correct? I realize that if I only wanted to solve a short first gear problem then a rear end replacement is the easy way to go and I have in fact done that by replacing my 4.083 with an Infiniti J30 3.9 with VLSD. (thank god). That helped a little bit, but what I realized is that the taller rear end, while enhancing my first gear experience, had a widening effect on the gap between all other gears. I'm afraid that going with an even taller rear end will exacerbate this issue. I'm trying to visualize in my head what a gap from 2.9 to 1.7 would be like. I guess I'd just have to try it to find out. What I think I want is a 2.9 first gear followed up by ~1.9 second gear. Changing the diff is far easier than rebuilding a trans. Although a trans rebuild is inevitable in my future. Thanks again guys.

Hey Stupid_fast, thanks for the response. I saw those Nismo gearsets outlined in some other posts on this forum. Is it not just a swap of the tailshaft section on the '71 trannies? Evidently not? I'm aware that my FS5W71C is regarded fairly well in the community however what i'm looking for is a tall and close ratio gearbox because I run out of first gear too quick. I need more speed and less torque. I'm running a turboed KA (which becomes a freakin torque monster on boost) @ 11psi and probably somewhere around 300HP, maybe a touch under that. I dyno'd 224HP @ 6psi, haven't dyno'd 11psi yet. Anyway, I appreciate your information. It does sound like it'll be an effort in futility trying to to piece this together. What I'm dreaming about is this http://www.frsport.com/Nismo-32010-RRS50-6-Speed-Transmission-SR20DET-S13-S14-S15_p_26092.html http://www.nismo.co.jp/en/products/competition/mission/silvia.html (same thing from two different web sites) Too bad it doesn't bolt up to a KA. IF ONLY!!! The ratios on this hybrid trans are (in case you didn't follow the links). Transmission 1st 2nd 3rd 4th 5th 6th NISMO Reinforced Cross 2.9071 1.9888 1.5373 1.2179 1.00000 .8624 Genuine 6-speed (FS6R92A) 3.6264 2.2000 1.5412 1.2132 1.00000 .76743 Genuine 5-speed (FS5W71C ) 3.3214 1.9023 1.3084 1.0000 .8378 - this is an S15 trans, built with the ratios I'm looking for, 6 spds, and a few other mods to make it USDM swap friendly. I just thought I would spend some time trying to see if I could recreate something close to this that would bolt up to my KA. In any event. I do appreciate any and all feedback from you or anyone else from your community. I'm a long time Nissan SR20/KA24 builder of both FWD and RWD vehicles and have been involved in my community since the late 90's. I won't take any information for granted. Thanks again

Hi Datsun community, I know this inquiry isn't exactly Datsun related, however there seems to be a lot of knowledge in this forum about transmissions. I'm wanting to create a close ratio gearset with a tall first gear. I've done some research and there appears to be these Nismo gearsets that apparently have existed with 2.9 first gears. There's also 81-83 280Z's with this gear combination apparently. My question is do all 'C series transmissions have interchangeable parts? And how on earth does one go about finding these Nismo gearsets? I can't seem to find them being sold anywhere. If I sourced a 280Z transmission would I be able to swap those gears into my 'C trans? Thanks guys Ben