OS Giken GTA Close ratio gear set - Alfa Romeo Bulletin Board & Forums
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post #1 of 63 (permalink) Old 03-21-2011, 09:22 PM Thread Starter
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OS Giken GTA Close ratio gear set

Am curious if anyone out there has built an Alfa Gear Box with the OSG GTA close ratio gearset and if so what their thoughts are on: form / fit / function.

Happy Motoring

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post #2 of 63 (permalink) Old 03-22-2011, 07:34 AM
Richard Jemison
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OSg gears

I thought you bought one???

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RJR Racing

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post #3 of 63 (permalink) Old 03-22-2011, 09:27 AM Thread Starter
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Originally Posted by Alfar7 View Post
I thought you bought one???
Foto is of the OSG close ratio gear set just before I put the case halves together. Wanted to see if other folks have had a similar experience.?

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post #4 of 63 (permalink) Old 04-29-2011, 10:58 AM
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I recently was in Merritt Carden's workshop in Newark, CA and he showed me an OS Giken gearbox for Alfas that was sent to him. The customer thought it was Merritt's gearbox but was mistaken. Merritt showed me several points on it that he deemed inferior. For one the gears are not hardened. Also the syncro teeth (not the slider, the ones next to the gears) are an integral part of the gear, so when they wear, the whole gear must be replaced, and this one was worn. He pointed out some other stuff that I could not understand. His opinion was that the thing is a piece of crap. If you want more info that I am relaying, give him a call and I'm sure you will get an earful.

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post #5 of 63 (permalink) Old 04-29-2011, 01:23 PM Thread Starter
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Stefano, appears there are a lot of things you don't understand, but thanks for your input none the less.
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post #6 of 63 (permalink) Old 04-29-2011, 02:03 PM
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Had the feeling the reaction here would be something like that. I really should have just said, Merritt Carden has the info you are asking, but is not on the BB. You can call and ask him.

Sorry if that is not what you wanted to hear. I know these things are expensive.

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post #7 of 63 (permalink) Old 04-29-2011, 05:40 PM
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Info?

The syncro assemblies are NOT part of the gear. If you look, machining such is impossible.

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post #8 of 63 (permalink) Old 04-29-2011, 06:13 PM Thread Starter
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Originally Posted by Alfar7 View Post
The syncro assemblies are NOT part of the gear. If you look, machining such is impossible.
Richard, Stefano has a lot to learn and is making some rather uninformed assumptions. If he's smart he'll listen to you and learn.

Thanks for jumping in here. Question to you: what is material, hardness and fabrication method of stock Alfa gears. Am assuming they receive some sort of post machining heat treatment or surface hardening? What is the surface hardness on the Rockwell B or C scale if you know it. You've machined a lot of them what's your opinion of their durablity and quality.?

The OSG gears are made from grain oriented Japanese steel forgings. The alloy is a JIS standard and I really haven't taken the time to search for it and cross reference it to American standards. They shot peen the gears also.
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post #9 of 63 (permalink) Old 04-29-2011, 08:28 PM
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The syncro assemblies are NOT part of the gear. If you look, machining such is impossible.
Yes, not machined as one. They are welded to the gear. Sorry for my choice of words. They cannot be separated from the gear. Once the syncro teeth are worn or damaged, the gear is worthless. This I saw for myself as it was being described to me.

Are those gears able to be separated from the syncros? If so, maybe they are not the same as the ones that were sent to Merritt.

The only assumption I made was about the hardness. I am assuming he is correct, which is not uninformed, as I have no reason to doubt him. He knows more about this than most people around.

Again, if those OS Giken gears are different, these observations don't apply. I have great respect for Japanese machining as I've visited some houses there several times. They take great pride in what they do. I was surprised to hear Merritt describe them as such actually.

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post #10 of 63 (permalink) Old 04-30-2011, 07:57 PM
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Gears

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Yes, not machined as one. They are welded to the gear. Sorry for my choice of words. They cannot be separated from the gear. Once the syncro teeth are worn or damaged, the gear is worthless.
No, they are not worthless, you simply machine out the syncro and weld in another.
Been doing this for years. It`s only metal

Alfa gears are surface hardened. The material machines easily below the surface hardwened layer. Most current gear builders are using various 9000 series alloys which are stronger and wear resistant without surface hardening..

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post #11 of 63 (permalink) Old 04-30-2011, 08:31 PM
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Quote:
Originally Posted by iachella View Post
I recently was in Merritt Carden's workshop in Newark, CA and he showed me an OS Giken gearbox for Alfas that was sent to him. The customer thought it was Merritt's gearbox but was mistaken. Merritt showed me several points on it that he deemed inferior. For one the gears are not hardened. Also the syncro teeth (not the slider, the ones next to the gears) are an integral part of the gear, so when they wear, the whole gear must be replaced, and this one was worn. He pointed out some other stuff that I could not understand. His opinion was that the thing is a piece of crap. If you want more info that I am relaying, give him a call and I'm sure you will get an earful.
lol

dude i 'll take that piece of crap off his hands anyday...

let me know how much he wants for it.

cheers

db
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post #12 of 63 (permalink) Old 04-30-2011, 08:42 PM Thread Starter
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Thanks for the clarification Richard. BTW: I owe you some dyno numbers, I haven't forgotten.

Also what does shot peening to high strength steel bring to the party? I suppose you get some stress relieving from it and / or surface hardness.?

9000 series steel has many different options but looking at the overall spec looks like the trend is a lot of chrome, nickel and silicon with really high tensile strength and modulus of elasticity in some of the options. Machinability aint that hot in some of the options which sort of figures with all the chrome and nickel.

Boron, B 0.000500 - 0.00300 % 0.000500 - 0.00300 % Average value: 0.00175 % Grade Count:4
Carbon, C 0.0700 - 0.650 % 0.0700 - 0.650 % Average value: 0.226 % Grade Count:88
Chromium, Cr 0.250 - 1.45 % 0.250 - 1.45 % Average value: 1.13 % Grade Count:67
Iron, Fe 93.7 - 98.4 % 93.7 - 98.4 % Average value: 95.2 % Grade Count:88
Manganese, Mn 0.400 - 1.10 % 0.400 - 1.10 % Average value: 0.644 % Grade Count:88
Molybdenum, Mo 0.0800 - 0.300 % 0.0800 - 0.300 % Average value: 0.121 % Grade Count:67
Nickel, Ni 0.250 - 3.55 % 0.250 - 3.55 % Average value: 2.94 % Grade Count:67
Phosphorous, P 0.0100 - 0.0350 % 0.0100 - 0.0350 % Average value: 0.0297 % Grade Count:59
Silicon, Si 0.150 - 2.20 % 0.150 - 2.20 % Average value: 0.665 % Grade Count:88
Sulfur, S 0.0100 - 0.0500 % 0.0100 - 0.0500 % Average value: 0.0380 % Grade Count:88

Machinability 40.0 - 70.0 % 40.0 - 70.0 % Average value: 49.3 % Grade Count:85

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post #13 of 63 (permalink) Old 04-30-2011, 09:14 PM
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Aren't synchro teeth part of all manual gearbox gears? ... thus why give this manufacturer such a hard time?
Pete

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post #14 of 63 (permalink) Old 04-30-2011, 09:35 PM Thread Starter
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Pete:

You said it yourself: "ps: Remember it's all just opinions "


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post #15 of 63 (permalink) Old 04-30-2011, 10:05 PM
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Quote:
let me know how much he wants for it.
I'll let him know when I see him next - should be in a month or so - and let you know.

I'll print out the discussion for him too.

Stefano
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