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OS Giken 5 speed close ratio gears

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Old 11-13-05, 11:45 AM
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OS Giken 5 speed close ratio gears

Does anyone has experience with this close ratio gear kit?

http://www.enonvativforce.com/close_gear.htm

http://www.osgiken.co.jp/pro_gear/mazda.html
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Old 11-15-05, 11:38 PM
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Nobody here ever used these gears? I've got a set I bought about the same time I bought my FD3S, but they're still in their boxes since I have still not ordered the parts needed to refresh my tranny, like new synchros, bearings and stuff.
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Old 11-18-05, 02:28 AM
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Nobody even hear/seem them before? No coments, anything?
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Old 11-18-05, 04:04 AM
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Pretty expensive. For those prices, I would be more interested in companies that could create a straight cut gear set to fit the stock tranny.
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Old 11-18-05, 11:59 AM
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Back then when I bought the kit, and that was like 3 years ago, they were pretty much the best I could find for the money, short of a Greddy kit or HKS gearbox. There was also a company in Japan named Adelia that carried close ratio sets, but I couldn't find a way to buy them, and besides, OS Giken was and still is a more reputable name in the business. They still seem to be the least expensive close ratio sets available for the stock FD3S gearbox, as the only other options available now are the Greddy and Guru (a.k.a. Xtreme Rotaries) kits, and both run above $6Ks.
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Old 08-04-07, 08:50 PM
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Right -- update on the Os Giken 5 speed kit. I have had it fitted, done 1000 miles without putting all 575 ponies through it and it's so smooth. I am now using it on full boost and it changes as sweet as a nut. Well pleased. I will be next out on track at Silversone on the full F1 GP circuit on the 2nd September, so I will update you on how it performs under track conditions.
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Old 08-04-07, 08:53 PM
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Got the Kit from these people.

https://www.rhdjapan.com/home/index.php

It's free to sign up etc.
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Old 08-06-07, 05:52 PM
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Someone I know with a 3 rotor used an OS gearset with good luck after breaking a couple stock sets.
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Old 08-06-07, 06:09 PM
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Originally Posted by CMonakar View Post
Someone I know with a 3 rotor used an OS gearset with good luck after breaking a couple stock sets.
Has your friend posted up the results anywhere, the reason I ask is that a friend over here has a 20b setup and he is running silly power. He needs to sort out a gearbox that will work.
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Old 09-22-07, 07:13 AM
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Originally Posted by WARTHOG View Post
Right -- update on the Os Giken 5 speed kit. I have had it fitted, done 1000 miles without putting all 575 ponies through it and it's so smooth. I am now using it on full boost and it changes as sweet as a nut. Well pleased. I will be next out on track at Silversone on the full F1 GP circuit on the 2nd September, so I will update you on how it performs under track conditions.
Just a quick update. F A N T A S T I C, P E R F E C T. So smooth and positive, enough said.
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Old 09-22-07, 07:30 AM
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Originally Posted by WARTHOG View Post
Just a quick update. F A N T A S T I C, P E R F E C T. So smooth and positive, enough said.
I am fitting one to my own FD soon
Has to be the best upgrade around with total streetability and little tomfoolery regards running a dog box.... pretty cheap for what you get too in my opinion.

www.rhdjapan.com
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Old 09-25-07, 09:42 PM
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Only problem is the gear ratio's suck for drag racing. There good for road racing I suppose.
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Old 01-26-08, 12:07 PM
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WARTHOG, great to finally know that somebody has got experience on this gear set and that it is working "F A N T A S T I C, P E R F E C T" for you. Please further enlighten us: did you replace from your gearbox anything else besides what came with the OS Giken kit, like new synchros, bearings, spacers, dowels, etc? Both the OS Giken promo and instructions literature mention a Mazda part # R502-17-316 (spacer) and R502-17-306A (roller bearing), did you have to use these parts? Anything else you had to do differently to what the Mazda shop manual instructs to?
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Old 01-26-08, 12:15 PM
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I have gone through 3 sets of them in the Falken RX-7 and the RX-8. We have had to look to other options for transmission for this season, especially with the new power added. I think they would be amazing used on road course, but they didn't do so good drifting.
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Old 01-27-08, 09:10 AM
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Originally Posted by EFINI_RX-7_RZ View Post
WARTHOG, great to finally know that somebody has got experience on this gear set and that it is working "F A N T A S T I C, P E R F E C T" for you. Please further enlighten us: did you replace from your gearbox anything else besides what came with the OS Giken kit, like new synchros, bearings, spacers, dowels, etc? Both the OS Giken promo and instructions literature mention a Mazda part # R502-17-316 (spacer) and R502-17-306A (roller bearing), did you have to use these parts? Anything else you had to do differently to what the Mazda shop manual instructs to?
Hi mate,
The only additional things you need are the OEM Mazda parts listed above and we fitted them. We did not do anything else as the kit is all there. It was a simple strip down and re-build.
I use my FD on the road 12 months of the year and on track. The Race Track I tend to use now is Silverstone F1 full track. It is very fast and the FD loves it. My db levels tend to be over what a lot of our Race Tracks will permit due to noise levels and tree huggers.
I have done the Nurb-Ring in Germany and it loves it. Even the wife ( Her Royal Sowness ) has commented on how much nicer the gearbox feels under full power.

I did a lot of searching for the answer to the problems of killing the FD gearbox, when you are laying down over 500bhp. There are a lot of different ideas and major projects around the world ( none of which are reasonable in price and time ). This option is just plug and play. I asked the lads in Japan what they do to resolve this problem and there was only one answer OsGiken. They have Fd's running 900bhp using this set-up with no issues on road/track.
I did not ask about the Drifting aspect I must admit as my set up is all about keeping it planted, I don't want it to let go on corners.

FC3S.Org---- It may be worth asking the Drifting lads in Japan what gearbox/internals they use.

Anyway hope that helps someone. Best Regards, His Royal Hoggness.
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Old 01-27-08, 09:15 AM
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As an after thought......

Is anyone using the new Aquamist Water Injection Kit for the FD ( I have put a thread up but no replies ).
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Old 03-26-14, 04:36 AM
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What rear diff ratio are you guys using with the os 5 speed?? I think I have a 3.9 ratio and it's a bitch to take off from traffic lights
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Old 03-30-14, 07:52 AM
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Bump anyone??
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Old 02-06-17, 08:02 PM
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So ive recently invested in a 5 gear OS set with mainshaft, its not going to be ready until mid year.
Just wondering what the tall 1st gear is like on the streets.

I believe stock 1st is roughly 3.5 while the OS 1st is 2.6
the stock 3.5 1st is pretty useless when you're putting out some horsepower, 2nd gear too - too low, no traction, spend more time shifting than making noise.
, but is the 2.6 a bit too tall for a nice launch with r-compound tyres, and general street duties?

edit. above post seems to answer my question. The os 1st gear is closer to the stock 2nd gear than 1st. I imagine it would be ok used in anger with generous amounts of clutch slip but could be a pig on the street. *sigh* Really dont want to go with a high ratio ring and pinion just to make 1st gear better.

Last edited by WANKfactor; 02-06-17 at 08:34 PM.
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Old 02-07-17, 05:31 PM
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I imagine it really depends on your turbo and engine set-up.

If taking off from a stop in 2nd gear isn't easy with your current set-up, well you know what you are in for...
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Old 02-07-17, 07:32 PM
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Hmmm. Thats what i was thinking too, and taking off in 2nd is a bit of a pig, but OEM 2nd is 2:1 and OS 1st is 2.6, Im just hoping that's enough to make all the difference.
I wish it came with something closer to a 3:1 1st gear.
Im sitting at 3000rpm at 100kph(60mph?) in 5th with the current set up just to give an idea of final drive, which seems ideal the way it is.

Here's a link with the ratios; RHDJapan : OS GIKEN Close Gear Kit 5-Speed + Main Shaft - FC3S

The other thing i need to look at next time im out in the car is what speed i can down shift to 1st in - as i imagine i will be wanting to do that from time to time with those ratios. My synchros are pretty much toast though so results may be inconclusive. Do you know if there is a lockout or something on 1st on the TII boxes?
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Old 02-07-17, 10:43 PM
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No lockout on 1st in the TII boxes.

My original (S4 short 5th) TII trans that lasted 160,000 or so miles before it sheared 3rd gear was always fine downshifting into 1st at auto-x.

My 2nd TII trans (JDM S4 ultra short 5th) never wanted to downshift into 1st without making grindy noises.

I always use this site when figuring out gearing.

Gear Ratio Speed Calculator

You can play with the engine rpm to see the speeds at which the shifts/downshifts will happen.
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Old 02-07-17, 10:51 PM
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Thats awesome, thanks. yeah, they are a bit hit and miss the t2 boxes. I've had a few and none were 100%. the plan is to try and build a really nice one when the gearset finally comes in.
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Old 02-08-17, 04:55 PM
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Originally Posted by WANKfactor View Post
So ive recently invested in a 5 gear OS set with mainshaft, its not going to be ready until mid year.
Just wondering what the tall 1st gear is like on the streets.

I believe stock 1st is roughly 3.5 while the OS 1st is 2.6
the stock 3.5 1st is pretty useless when you're putting out some horsepower, 2nd gear too - too low, no traction, spend more time shifting than making noise.
, but is the 2.6 a bit too tall for a nice launch with r-compound tyres, and general street duties?

edit. above post seems to answer my question. The os 1st gear is closer to the stock 2nd gear than 1st. I imagine it would be ok used in anger with generous amounts of clutch slip but could be a pig on the street. *sigh* Really dont want to go with a high ratio ring and pinion just to make 1st gear better.
Hey WANKfactor, who did you ordered the kit from? And how long to shipped after ordering? I am looking to get the 5 gear OS set with mainshaft for the FD3S. NENGUN is advertising the kit for a little over $2200 and one year turn around time.

My car is set-up for autocross and I have 4.77 rear gear ratio.
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Old 02-08-17, 04:57 PM
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Hey buddy. I ordered mine from RHD Japan, 225k yen, 8 month wait.
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