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

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.

Nobody even hear/seem them before? No coments, anything?

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.

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.

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.

Got the Kit from these people.

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

It's free to sign up etc.

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.

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.:icon_tup:

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

Only problem is the gear ratio's suck for drag racing. There good for road racing I suppose.

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?

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.

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.:lol2:

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 ).

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

Bump anyone??

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.

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...

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?

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.

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.

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.

Hey buddy. I ordered mine from RHD Japan, 225k yen, 8 month wait.

I bought a jdm FD motor and trans and it came with an OS giken twin plate and a close ratio gear set.
If you thought the jdm gearbox was short already, try cruising on the highway at 3500rpm :D

^ Do you have a short ratio diff? According to the chart, oem 5th is .8 and OS is .82, not that radical a difference?

How do you find taking off in 1st gear? Is it ok or is it a pig?

edit; what speed are you doing at 3500? so i can do a calculation and compare.

Ok, thanks for the info.

I should get my car back in the next couple of weeks with os gearset and 4.77. I still have factory twins and with good diff center and suspension even with lighter flywheel i think it might only just turn the tyres through the top of 1st when cold. Short top will be a bit annoying but if I manage to twin charge it next year I will swap the 4.1 gears back in or maybe even the auto gears.

^ sounds good. Keep us updated. I'm still waiting for mine. Ordered mine through RHDJapan about a year ago. Was supposed to arrive mid year, then september, now they have pushed it back till feb. I'm a bit worried about it.

Maybe talk to Marcus, he buys batches of them in. I got lucky, Ric usually keeps a set on the shelf, i was actually going to wait and try grafting a corvette box/diff assembly into it when i was settled into my cousin's place in Melbourne with shed/hoist/welding bay but it developed an oil leak from the box and i cracked the shits and decided to stay bolt in. Marcus has sold a heap of diff rebuilds to guys with OS gears with the cusco lsd, solid pinion spacer and 3.9 auto gears and recons they love it.

having bolt in multiplate clutch options with standard gear is nice, I would have had to remake the tunnel, get half shafts, make a torque tube etc. Rear bias weight distribution would have been good for traffic light battles or the strip thpugh.

Pretty happy on first impressions.

Is a bit noisier than standard box but I have a hard mounted gearbox brace, will swap it out for rubber isolated one in time.

the new sycros are good, should keep improving for a while too. Still no Supra 6 speed getrag though.


the ratio splits are excellent for power down. I have the 4.77 gears with stock 255/35 R17 s8 fd rear end works well. Revs more at cruise but ratios are better for performance.


I wouldn't have thought coilovers and the diff would improve power down as much as they did either, really happy with how it drives.

Good to hear youv'e got it all happening and it works well. I hope mine eventually comes in sometime during my lifetime! Im really looking forward to having a long 1st gear that i can actually use and all the flexibility of the close ratios in between.
Just out of curiosity so i can compare - what rpm are you pulling in top gear at 100kmh and how are you finding 1st gear in general?

With the shorter diff it will be getting close to 4000rpm at 120. I have a lighter flywheel and ceramic clutch to get used to still but the taller first is a better gear. I'm hoping when I go Single/twin charged on WI I will have heaps more torque everywhere so may swap the factory diff gears back in if cruise annoys me. I don't think it will be an issue if not freeway driving a lot.

I'm guessing your rolling radius on the older car will be a bit smaller and lighter chassis so 1st with standard or close to standard gears should be good. 5th itself is only 3% shorter so probably won't bother you cruising.

Well thats good 1st gear isnt a pig. Sounds like your final gearing is a touch shorter than mine with 225/45/15 and 4.1 . Cant wait for progress on your fancy twin charge setup!

Why wouldn’t you just get the Par-Engineering gearset which includes WPC treatment and free custom gear ratios with an 8 - 12 week built to order lead time?

All ears for feedback on PAR. Straight cut/dog engagement is mega noisy /not real practical in a street car though, if you go syncro /heli cut not a lot of difference and if you option 5th you end up more expensive than OSG. Heard about several PAR and PPG fails in the past but it is always hard to tell what is going on, factory cases will only ever deal with so much too.

If you knew you were unlikely to get out of 4th on track and had short diff gears the taller 5th of the PAR is probably desirable. I wanted something immediately and Ric had it on the shelf.

I'm very happy with this box so that is good enough for me.

I forgot to mention free helical gear option. You have no excuses, sorry ... :)

Well if you had of mentioned them earlier..... Pretty expensive though.

800rwhp/550tq on par

Stock case?

About $2000 USD for 5 speed giken.

If it’s suitable for your needs then sure. I don’t think the engineering and material selections are quite on par with Par (hehe) but if you don’t need that level and don’t mind waiting until whenever then no need to go there. It sounds like OSG is a good set, but you get a lot of flexibility, WPC treatment, gear options, and a real build to order completion date on the PAR that provide a bestoke product for a reasonable price.

Yeah the time factor is a concern. If i had have know they were this slow i would have looked at other options. But price was a big factor. I was not aware of the PAR stuff untill you mentioned it, but there are other options at that price point too, but seriously, if i wanted a stronger synchro, heli cut box at that price point, i would be looking at something other than a mazda box altogether.

If you are in a factory case race class it would definitely be a good option. I wanted to stay close to OEM if I could, If i ever break this one it will be a tremec 6 speed which will give me a genuine cruise gear and similar 1-5 ratios or chopping a corvette "its not a transaxle" or similar into the back for that kind of money.

I hope you don't have to wait too much longer Wankfactor. Welcome to my factory gearset if you manage to bust yours in the mean time.

Monsterbox, how many rotors and s it an even fire engine? A box should be able to take near twice the "average" torque from a 4 rotor as it will from a 2 rotor as it is generally the peak impulse that kills them. Big advantage of making a power figure with a 3 or 4 rotor is less clutch/box required compared to a 2 rotor.

Its due end of Jan now. Thanks for the offer Slides, but i will probably try and get hold of a complete 2nd hand box for backup in case that happens.

One of the cars that ran a PAR here, the mechanic ended up cutting a hole in the body to speed up "rectification" work on the shift mechanism that happened at virtually every session during each meeting. Ended up biting the bullet in frustration "putting" a Hollinger in the stock case eventually....where the case there just accommodated the input quill, which is about all it's good for. :biggrin: Reality is, stock cased gearsets are pretty much a joke if you're doing anything half-serious - track day warrior might just be ok, OS will eventually shit the bed too......but for other reasons.

The thing I forgot to mention though is the Par pricing is a single gearset built to order. So that one gearset is covering all the machining setup etc. I think if a group of people offered a multi-gearset order that the price will drop more than you might think ...