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OS Giken gear set for FD

Old 01-10-09, 04:31 PM
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OS Giken gear set for FD

Does anyone have track experience with these gears? I ran the ratios through a calculator and even with a 4.7 rear end they are extremely tall (think 1st goes to 50mph+) and I'm not sure if I would like them ontrack if I had to go down into 1st for some really slow corners, since the syncro won't let you in unless you're doing 15mph so I'd have to double clutch.

-Andy
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Old 01-11-09, 11:15 AM
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I don't know much about the OS Giken ratios but there are other options in that price range...

Quaife...

http://www.autotech.com/quaife/index2.htm

Guru (Australian)...

http://www.xtremerotaries.com/main2/guru/gearbox.htm

The above list gear ratios for comparison. There are other Japanese gear sets but most are even more expensive.
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Old 01-11-09, 04:28 PM
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Ok, Ive seen the Guru gears before, I don't want them as it converts to dogbox, but I didnt know Quaife had a set for the FD, I'll run them through the calculator. Thanks

-Andy
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Old 01-11-09, 10:41 PM
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Grassroots Motorsports just did a comparo of rear diffs on a Honda S2000 - stock Torsen vs. OS Giken vs. Kaaz. Might want to check it out.
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Old 01-12-09, 02:24 AM
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Originally Posted by gracer7-rx7 View Post
Grassroots Motorsports just did a comparo of rear diffs on a Honda S2000 - stock Torsen vs. OS Giken vs. Kaaz. Might want to check it out.
Cool thanks man, i read it, that OS Giken rear end really is great. I'd put one in the car but just a year ago my buddy and I built a super Turbo II clutch type for my car perfectly clearanced and all new wear parts, if I could find a way to exchange that for the OS without too much cost to me it'd be great but I don't really want to given that I just spent that money! If their gear sets are as good as their diffs then maybe I should check them out though. What have you been up to? still trackin the FD? My comp was a bit low, I had a stuck side seal and my turbos were goin out so I decided to do a major rebuild + single turbo! Look for a build thread soon I'm not pulling any punches on this one!

-Andy
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Old 01-12-09, 09:58 AM
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fwiw - most people I see changing rear gear ratios are either autox or drag guys.

IMO:
Unless it is a full on race car or autox/drag car where every lap counts, I just don't see going to 4.7 as worthwhile IF you do a fair amount of street driving. I'd probably go no higher than the 4.3 of the JDM cars. I'm perfectly happy with the stock 4.10 with the shorter 5th gear of the JDM / 99+ tranny. Its up to you though.

I've been up to my eye ***** in work and life. Besides that Fd has been fine and I've been driving it on Skyline whenever I get a chance. Haven't turned a wrench on it in months other than re-installing my Konis after Tripoint rebuilt and revalved them. Looking forward to a good amount of track time in 2009.

Good luck with the build.
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Old 01-12-09, 05:50 PM
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Originally Posted by gracer7-rx7 View Post
fwiw - most people I see changing rear gear ratios are either autox or drag guys.

IMO:
Unless it is a full on race car or autox/drag car where every lap counts, I just don't see going to 4.7 as worthwhile IF you do a fair amount of street driving. I'd probably go no higher than the 4.3 of the JDM cars. I'm perfectly happy with the stock 4.10 with the shorter 5th gear of the JDM / 99+ tranny. Its up to you though.

I've been up to my eye ***** in work and life. Besides that Fd has been fine and I've been driving it on Skyline whenever I get a chance. Haven't turned a wrench on it in months other than re-installing my Konis after Tripoint rebuilt and revalved them. Looking forward to a good amount of track time in 2009.

Good luck with the build.
Yeah I already have the 4.3 rear end and plan to stick with it, I was just trying to comprehend how the OS gears could be so much taller than stock. I think they might be for a hardcore racecar that's really fast with aero and would always be going faster than first gear. My car will be converted to a mainly track car with some compromises made for streetability, I will most likely just run the JDM fifth gear.

Cool, did you go with the Tripoint coilover conversion? I'm going to give the RE-A DG-5 coilovers a try, but I was also interested in the tripoints. Lately I've just been enjoying the easy stock nature of my M3.
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Old 01-12-09, 09:28 PM
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a friend used the OS giken gear ratio. If you are planning over 500whp you will end up braking it...
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Old 01-12-09, 10:25 PM
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Originally Posted by R-R-Rx7 View Post
a friend used the OS giken gear ratio. If you are planning over 500whp you will end up braking it...
Really, I thought it was supposed to be stronger than the stock gears and they can handle 600?
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Old 01-12-09, 11:23 PM
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The OS Giken should produce more friction than the stock Torsen. What that would do to the longevity of the various parts of the rear diff is beyond me. People say the stock FD dif will also break under high HP so go figure...

I don't have the expensive Tripoint setup using the Koni race shocks. I just had my off the shelf Koni Sport adjustables rebuilt and revalved to the spring rates I was using.
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Old 01-13-09, 01:06 AM
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Originally Posted by aoc007 View Post
Really, I thought it was supposed to be stronger than the stock gears and they can handle 600?
what makes u need one anyway? You can achieve the same results with a lot lower budget with a shorter gear ratio
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Old 01-13-09, 01:22 AM
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Originally Posted by R-R-Rx7 View Post
what makes u need one anyway? You can achieve the same results with a lot lower budget with a shorter gear ratio
I'm not sure what you're talking about? A rear end ring gear change?

Originally Posted by gracer7-rx7 View Post
The OS Giken should produce more friction than the stock Torsen. What that would do to the longevity of the various parts of the rear diff is beyond me. People say the stock FD dif will also break under high HP so go figure...

I don't have the expensive Tripoint setup using the Koni race shocks. I just had my off the shelf Koni Sport adjustables rebuilt and revalved to the spring rates I was using.
As long as the stock diff isn't abused (wheel hop, hard launches, too high of tq going through it) it should last forever when properly maintained, torsens use worm gears that don't really wear. The OS Giken will eventually wear out because it uses clutch plates. Although it will wear much less than a normal clutch-type because it is able to full lock up because its a hybrid with a locking diff and it uses a lot more plates than most clutch-types.
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Old 01-13-09, 09:56 AM
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^Good explanation. Learned something new.
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Old 01-13-09, 10:18 AM
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I wish Quaife made a diff for the FD.
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Old 02-02-09, 01:11 PM
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Anybody know the part number to the 99 spec fifth gear?
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Old 02-02-09, 01:16 PM
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Its the same as a TII I believe
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Old 02-05-09, 10:41 AM
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Hmm, interesting, thank you sir.
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Old 02-05-09, 11:05 AM
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OS Has impeccable quality. I would deff lean toward their products.
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Old 02-15-09, 12:46 PM
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I know of someone over here who runs this gear set and is very impressed with it
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Old 02-16-09, 01:18 PM
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Originally Posted by afgmoto1978
Anybody know the part number to the 99 spec fifth gear?
Dizzy going back and forth between an English and Japanese parts resource, but this should work....there's a couple of ratios

normal overdrive 5th (17-611), R523-17-610

jap spec to suit 16" wheel R507-17-610C.....to suit 17" wheel R512-17-610B....were about 11,900 yen before tax.

countershaft overdrive (17-308), R524-17-308

jap 16", R507-17-308......17", R513-17-308 ~ 7550yen.

Originally Posted by afgmoto1978
I wish Quaife made a diff for the FD.
There is a vendor down here who used to do a torsen upgraded centre, apparently wouldn't consider doing another run unless there was a small run order made though.
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Old 02-17-09, 09:32 PM
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Nice, thank you sir.

I would be so down for that, but knowing how little the 7 community knows of Quaife and their product, few would sign on. Even though they would be getting a diff that's superior to the clutch type units. What was the company who did it if you don't mind me asking?
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Old 02-18-09, 01:44 PM
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Company was Pfitzner in South Australia, going off rough memory of someone else's swap a couple of years back, think a figure around aud$1~1.5k was the going rate, but they wanted a run of 10(?) units. No idea if they change the bias ratio....apparently will guarantee against breakage though. Contact should be Tim Possingham if you want to email them, he was the Mazda gearbox guy about 3 years ago at least....unless he's left in the meantime.

Found out the 17" wheel 5th gear ratio is .763, so in between the .806 base domestic and .719 export market ratios. Here's the plot with standard tyre/diff combos for the relevant models...

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Old 02-21-09, 05:03 AM
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Originally Posted by aoc007 View Post
Its the same as a TII I believe
The T2 5th is .719 ratio, just like USDM FD 5ths.

Dave
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