Rosco Posted November 17, 2014 Share Posted November 17, 2014 (edited) I have a 280Z track car with a built L28 and a 240sx trans, it has a OS Geiken LSD (not sure the gear ratios). Id like a trans with a taller first, closer second and third and a shorter fifth than the sx trans. can I get gears for the sx trans and build it? is there a trans out there that fits the bill that will bolt in with little modification? or a lot of mods? Any guidance will be much appreciated. I'm shifting to fith at about 120mph, hp peaks at 7,300+/- rpms 357hp @ flywheel300ftlb torque @flywheel16" wheels with 245/45z R6's Stock gear ratio diff with OS Geiken LSD (not sure of ratio, one search says 3.54 another says 3.36)I have that SX trans in it now and if 2nd and 3rd were closer and 5th was a little shorter it would be great. Custom built dog box with straight cut gears is about $7-8k Budget is about $4-5k Edited November 18, 2014 by scobuggy Quote Link to comment Share on other sites More sharing options...
rturbo 930 Posted November 17, 2014 Share Posted November 17, 2014 Well it isn't cheap, but... http://www.rhdjapan.com/os-giken-close-gear-kit-5-speed-nissan-sr20det-fr-main-shaft.html 1 Quote Link to comment Share on other sites More sharing options...
Phantom Posted November 17, 2014 Share Posted November 17, 2014 (edited) Take a look at the gearing that came with the '82 & '83 280ZX. They were designed to go with a 3.90:1 differential so 1st & 2nd are slightly taller than the early 280Z 4 & 5 spds with closer ratios through the first 4 gears and roughly a .75:1 5th gear overdrive. I don't know the 240SX tranny gearing so you'll need to have all the numbers to make a decision as to whether a stock tranny can do it for you or if you'll have something custom built. Edited November 17, 2014 by Phantom Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 18, 2014 Share Posted November 18, 2014 "Best"? Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 18, 2014 Author Share Posted November 18, 2014 (edited) Best synonyms: most advantageous, most useful, most suitable, most fitting, most appropriate; most prudent, most sensible, most advisable Edited November 18, 2014 by scobuggy Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 18, 2014 Author Share Posted November 18, 2014 (edited) This http://www.rhdjapan....main-shaft.html unit won't work with the SX trans according to OS. But thank you for the link Edited November 18, 2014 by scobuggy Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 18, 2014 Author Share Posted November 18, 2014 (edited) SX trans 1st gear: 3.321 2nd gear: 1.902 3rd gear: 1.306 4th gear: 1.00 5th gear: 0.759 81-83 zx trans 1st gear: 3.062 2nd gear: 1.858 3rd gear: 1.308 4th gear: 1.00 5th gear: 0.745 This I'm sure is a dumb question but I don't quite understand the ratios. Which out of these two is a closer gear ration more suitable for a track car? Edited November 18, 2014 by scobuggy Quote Link to comment Share on other sites More sharing options...
clarkspeed Posted November 18, 2014 Share Posted November 18, 2014 Depends on a lot of things. Tire size, diff ratio, top speed at track, RPM's in important corners at track, power of engine, how hard and fast you want to shift, Availability of parts, and finally, how much you want to spend. For example, that ZX tranny you listed above is a good compromise, but if your gearing and track requires you to shift to 5th at 110+ mph, it sucks. 1 Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 18, 2014 Author Share Posted November 18, 2014 Too many factors I guess. I'm shifting to fith at about 120mph, hp peaks at 7,300+/- rpms 357hp @ flywheel 300ftlb torque @flywheel 16" wheels with R6's Stock gear ratio diff with OS Geiken LSD (not sure of ratio, one search says 3.54 another says 3.36) I have that SX trans in it now and if 2nd and 3rd were closer and 5th was a little shorter it would be great. Custom built dog box with straight cut gears is about $7-8k Budget is about $4-5k Quote Link to comment Share on other sites More sharing options...
Tony D Posted November 18, 2014 Share Posted November 18, 2014 There is no "best", it depends on the application and individual. Where have I read that before? It was someplace here... Quote Link to comment Share on other sites More sharing options...
rturbo 930 Posted November 18, 2014 Share Posted November 18, 2014 This http://www.rhdjapan....main-shaft.html unit won't work with the SX trans according to OS. But thank you for the link What makes you say that? COMPATIBILITY NOTES: Compatible Engine: SR20DET (FR) Compatible Transmission: FS5W71C The 71C is the SX trans, and aside from the bellhousings, they are otherwise identical, from what I've read. Take a look here http://forums.nicoclub.com/diy-swapping-sr-bell-housing-to-ka-transmission-t278158.html Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 18, 2014 Author Share Posted November 18, 2014 I called OS Geiken and asked if it would work in my SX trans. The guy told me it wouldn't. Maybe I should call back and talk to someone else. Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 18, 2014 Share Posted November 18, 2014 A higher numerical rear drive ratio will make the gears feel closer, and shorten the top end. You could probably get what you want with a different gear set in the back. You'll have to figure out what you have now first though. The ZX trans has closer low gears but a taller 5th. So you'd still need new gears in the back for the last shift. How do you get 357 HP, 300 ft-lbs torque, out of a non-turbo L28? That's some kind of "built". Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 18, 2014 Author Share Posted November 18, 2014 (edited) Someone mentioned a 4.11 rear diff, I don't know where you'd get a 4.11 though. I'm running a Rebello 3.2 on 110 octane, ITB's and 3" exhaust Edited November 18, 2014 by scobuggy Quote Link to comment Share on other sites More sharing options...
rturbo 930 Posted November 18, 2014 Share Posted November 18, 2014 I called OS Geiken and asked if it would work in my SX trans. The guy told me it wouldn't. Maybe I should call back and talk to someone else. That's odd, everything I've read online suggests that it should fit. Maybe the guys on Nicoclub would know more? Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 18, 2014 Author Share Posted November 18, 2014 It would be nice if it would fit, I'd order one today! I'll poke around a little if I can find the time and see what I can find out. Quote Link to comment Share on other sites More sharing options...
NewZed Posted November 18, 2014 Share Posted November 18, 2014 (not sure of ratio, one search says 3.54 another says 3.36) You're talking about spending $5,000 and you're not even sure what you're working with. Not good. Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 18, 2014 Author Share Posted November 18, 2014 I'll figure it out before I spend anything. That's one reason I'm on here. I'll rotate the half shaft and figure out what I have. Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 18, 2014 Author Share Posted November 18, 2014 You're talking about spending $5,000 and you're not even sure what you're working with. Not good. Good observation, Thank you for your concern Quote Link to comment Share on other sites More sharing options...
clarkspeed Posted November 19, 2014 Share Posted November 19, 2014 I dont recommend shifting at 120mph. The CD alone will wipe 10-15 mph off combined with a poor 5th ratio will put you in a hole. Your options are to find a better 5th gear box, change gearing where you shift to 5th at lower speed, or change gearing so you can stay in 4th. With a $5k budget you might get into a used Jerico 4sp with convert parts from Taylor. Or convert a WC T5. Quote Link to comment Share on other sites More sharing options...
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