Rosco Posted November 19, 2014 Author Share Posted November 19, 2014 Well it isn't cheap, but... http://www.rhdjapan.com/os-giken-close-gear-kit-5-speed-nissan-COMPATIBILITY NOTES: Compatible Engine: SR20DET (FR) Compatible Transmission: FS5W71C - S15: 5MT Models-fr-main-shaft.html FYIThe rep at OS Geiken says they have lots of complaints about this websit giving out false info. He said the close ratio gear kit is for an sr trans not a ka trans. He said they're working on a kit for the ka but it's still in the design stage. He wouldn't say if it would work with a little modification but did say there are subtle differences. I don't have the money to experiment. Do you know if the bell housing that was modified for my ka will fit on the sr? Quote Link to comment Share on other sites More sharing options...
rturbo 930 Posted November 20, 2014 Share Posted November 20, 2014 (edited) Weird, you'd think that being the same trans (FS5W71C) the internals would be the same, but OSG would know better than I do. I still find that strange, though. I really don't know about the bell housing. If the KA and SR bell housings can be swapped, you would think an L bell housing could be put on the SR trans too, but I really can't say. I'd really like to see someone take apart a KA and SR 5spd and compare the two. Edit: http://forums.nicoclub.com/ka-vs-sr-tranny-t391988.html Apparently the input shaft is slightly different - From the last post: the ka input shaft is slightly smaller after the splines it necks down where the sr input shaft does not do this and is a thicker Edited November 20, 2014 by rturbo 930 Quote Link to comment Share on other sites More sharing options...
Nelsonian Posted November 20, 2014 Share Posted November 20, 2014 There are some differences in the actual thickness of the gears in the S15 gear box compared to the earlier S14/13 boxes. The gears are 3mm thicker. Got that from another member here (Nigel) with a nice write up on Motortopia, when I was heading down the 98' S15 path. Quote Link to comment Share on other sites More sharing options...
duragg Posted November 20, 2014 Share Posted November 20, 2014 How much you raced this car yet? Road racing? Which tires? My 3L Rebello has a 4.38 rear drive The 71b tranny is light. Weight is the enemy. Sometimes the 5th is an issue so I am building a "1980" 71b. I have a whole wall of $50 71b trannys for backups which leaves me a lot more money for tires... Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 20, 2014 Author Share Posted November 20, 2014 (edited) About once a month Road courses with Hoosier R6's What came with a 4.38? SX trans is heavy and long What do you mean "Building a 1980 71B?" Do they make a gear kit for it? Edited November 20, 2014 by scobuggy Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 20, 2014 Author Share Posted November 20, 2014 (edited) Damn thing won't let me post sometimes??? Edited November 20, 2014 by scobuggy Quote Link to comment Share on other sites More sharing options...
duragg Posted November 20, 2014 Share Posted November 20, 2014 What size R6? New ones or old? TT or wheel-wheel race? You have aero? Post a pic of car? (Helps with overall picture) #1 you need to figure out your exact ratio by examining your ring gear ideally. Or if unwilling to do that take your exact rear tire size and RPM in 4th gear at a few different speeds and do the math. You probably make about 275whp like mine and a rear ratio of 4:11 might really wake things up. Quote Link to comment Share on other sites More sharing options...
duragg Posted November 20, 2014 Share Posted November 20, 2014 Early Z 71b 5 speeds actually had good close ratios for 3, 4 and 5. But a big gap for 2-3. 81-83 "close ratio" 71b had close 1, 2, 3 and 4 but a but gap to the .745 OD. They have some other nice improvements too like the reverse lockout. In 1980 a few "close ratio" boxes were made with. .77 OD instead of the .745. Every little bit helps. Quote Link to comment Share on other sites More sharing options...
rturbo 930 Posted November 20, 2014 Share Posted November 20, 2014 What do you mean "Building a 1980 71B?" Do they make a gear kit for it? Actually, they do. 77-79 71Bs had a .864 5th gear. http://www.rhdjapan.com/kameari-super-close-gear-set-l-type-fj20et-hr31-zenki.html Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 20, 2014 Author Share Posted November 20, 2014 Early Z 71b 5 speeds actually had good close ratios for 3, 4 and 5. But a big gap for 2-3. 81-83 "close ratio" 71b had close 1, 2, 3 and 4 but a but gap to the .745 OD. They have some other nice improvements too like the reverse lockout. In 1980 a few "close ratio" boxes were made with. .77 OD instead of the .745. Every little bit helps. 245/45/16 R6 Do you have a source for the Nissan comp close gear ration trans? Supposedly this 32010-N3130 was a factory comp trans with 2.907, 1.902, 1.308, 1, 0.864 Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 20, 2014 Author Share Posted November 20, 2014 What size R6? New ones or old? TT or wheel-wheel race? You have aero? Post a pic of car? (Helps with overall picture) #1 you need to figure out your exact ratio by examining your ring gear ideally. Or if unwilling to do that take your exact rear tire size and RPM in 4th gear at a few different speeds and do the math. You probably make about 275whp like mine and a rear ratio of 4:11 might really wake things up. 245/45/16 Used TT, track days, hpde's. Wish I had time to race, this z is so modified though I don't know what class it would be in Forgive me but I don't know what aero is? I'll post a pic when I get home. And I'll figure out what I have for diff ratio. A shop out in CA suggested a 4.11 diff Quote Link to comment Share on other sites More sharing options...
duragg Posted November 20, 2014 Share Posted November 20, 2014 (edited) An .864 5th would be killer on the later "Close ratio" trans, but because the counter gears are different you only end up with the .77 OD (aka 1980 box). A 4.11 would be great for you and you might be happy with it. If you are running a 3.54 or something now it will be like night and day. Or at least it was for me. Spending real money on a 71b just seems crazy to me. With my 4.375 I am almost never in 2nd gear, usually 3,4 & 5 so I may go back and try an early configuration in which 3,4 5 are tight. Here is some 2, 3, 4 & 5th gear action from NASA Nationals at Sonoma a few weeks ago. I had already won my region and was just trying to stay out of trouble at this event, so no heroics. http://youtu.be/fWbLrWAI4j0 Edited November 20, 2014 by duragg Quote Link to comment Share on other sites More sharing options...
johnc Posted November 20, 2014 Share Posted November 20, 2014 Having spend $8K on a Quaife Sierra dog box sequential from Taylor Race Engineering I suggest you call and talk with them. A $5,000 budget will probably get you a Jerico or a modified BW T5. But, be forewarned, you better know your rear gear ratios, tire OD, engine peak torque rpm, peak horsepower rpm, rpm limit, car weight, clutch, etc. before you call Taylor. They are going to ask you all of hose questions and more. And your car is undertired given your horsepower numbers. A 3:36, 3:54, or a 3.90 rear gear is completely wrong given your tire size, engine power, and rpm limits. You should be running at least 4:11 or 4:38 and probably a 4:64. Gear the car for a top speed of 150mph which will be about your limit on any track in the US except Road America and Road Atlanta. A 2.25 first gear would be a good starting point for your ratio selection. Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 20, 2014 Author Share Posted November 20, 2014 Here are a couple pics and a video of me at Road Atlanta a few months ago, Track day with Rezoom motor sports Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 21, 2014 Author Share Posted November 21, 2014 (edited) Where can I get a 4.11 diff? I guess I can research it… Thanks for all the info Damn site won't let me quote!! Edited November 21, 2014 by scobuggy Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 21, 2014 Author Share Posted November 21, 2014 (edited) I have an OS Geiken LSD in it now, 1. Can I get the 4.11 gear and reuse my LSD? 2. Where would I get just the 4.11 gear? Edited November 21, 2014 by scobuggy Quote Link to comment Share on other sites More sharing options...
johnc Posted November 21, 2014 Share Posted November 21, 2014 The site is fine. The sources for the gears have been posted here for 14 years. Please search. Quote Link to comment Share on other sites More sharing options...
johnc Posted November 21, 2014 Share Posted November 21, 2014 Based on the video you are geared way wrong. You appear to never go beyond about 6,000rpm. Based on your induction and claimed horsepower numbers you should running the motor to 7500 rpm or more. Quote Link to comment Share on other sites More sharing options...
beermanpete Posted November 21, 2014 Share Posted November 21, 2014 I have been thinking about transmission gearing as well. What are the options for mixing and matching the OE parts between variants of the 71B? Is it possible to move the input gear set from one year 71B to another year 71B to chagne the spread? What about 5th gear? What about mixing parts from 4-speeds and 5-speeds? Since the counter shaft is a single part incorporating all 3 low gears, has anyone made a new shaft the allows using gears from a 3rd partry like Jerico? Quote Link to comment Share on other sites More sharing options...
Rosco Posted November 21, 2014 Author Share Posted November 21, 2014 Quote Link to comment Share on other sites More sharing options...
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