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Getting a 4.875 Ring and Pinion for FC...

Old 04-13-07, 12:15 PM
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Question Getting a 4.875 Ring and Pinion for FC...

I'd like to change the stock 4.10 ring and pinion to a 4.875. Does anyone know where I can get this done or who/what company will sell me an assembled unit.

It'd be great if the place had the ring and pinions and did the work as opposed to buying it and shipping it off to someone and then getting it done. Racing Beat sells the ring and pinion for $415 before shipping, but who will do the work.

Thanks,
K

msn: Kamui ([email protected])
aim: EBXKIX

Btw, this is a street car and not a track only car.
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Old 04-13-07, 02:55 PM
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the 5.12 is a better choice and more popular but I see your application is also for a street car. Try www.iscracing.net for a lead. They don't do them but have a source that does. He has a 5.12 lsd new and complete - $2450. Try www.improvedtouring.com as well and maybe someone has a 4.88 laying around.
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Old 04-13-07, 11:54 PM
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Thank you
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Old 04-14-07, 12:11 AM
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I have done this with my FC. I recently sold the complete S4 Diff with 4.88 gears and posi (Mazda Comp parts) to Louis of Rotary Reliability & Racing.

Sylvain Trembly of Speed Source Racing set me up with the custom setup. About $1500.00 including shipping from Florida to Nevada (had to ship my stock differential to them - about 2-3 weeks turn around time).
Very high quality work. Never had any problems with the differential. Had everything powering it from NA steet ported, Camden supercharged to 500 hp V8. Didn't use it too much with the V8 - way too steep ran out of gear at the 900 ft mark.

Project build progress:

https://www.rx7club.com/rx-7-audio-visual-lounge-143/1987-supercharged-fc-457752/


SPEED SOURCE RACING

http://www.speedsourceinc.com/


One of the best performance mods I did for improving acceleration - especially when NA.

Last edited by katorx7; 04-14-07 at 12:19 AM.
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Old 04-14-07, 09:01 AM
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Thanks katorx7 I just send a message to Sylvain hopefully they'll still do the work with their busy schedule. I've already contacted ISC Racing Services (the only people I knew used to do the work) and they only do a handful of 5.12's now. I really hope I find someone that still does it.

K
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Old 04-14-07, 09:15 PM
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I remember we just had this conversation on another forum, see this thread... it's got 2 leads in it for you. http://itforum.improvedtouring.com/f...&hl=5\.12&st=0


Andy - www.flatout-motorsports.com
seckerich - he doesn't have a shop to my knowledege so you'll need to post on the thread


.. I got lucky and found my 5.12 on this board.
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Old 04-14-07, 09:46 PM
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Speaking of that 5.12, how you doing with it?
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Old 04-15-07, 08:26 AM
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Originally Posted by jgrewe
Speaking of that 5.12, how you doing with it?

What a difference! Very much worth every penny for anyone considering one, this is a MUST item for any race car. Now if I can only learn to drive... hopefully it'll be ready for a month end NASA race.

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Old 04-15-07, 10:10 AM
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AWR is able to do ring and pinion stuff. I have a freind who races an EProd and from what I understood they took two pnion shafts and had to splice them back together. I dont know why they had to do this in his case, but if they can machine, weld, and re-heat treat the gear set then I think they can do just about anything. I think he mentioned costing something like $1,700 all together.
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Old 04-15-07, 03:08 PM
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Thanks, I'll shoot AWR an email in a bit. I should've just bought one when I first thought about it instead of waiting...this is beginning to be an adventure I might end up driving the car before I get it anyway.

K
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Old 04-15-07, 08:04 PM
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Thumbs up

I have purchased a Gen one 4:88 to 1 gear set to install in to a Gen two third member. This was done to meet the ICSCC technical requirements for the RS (Radial Sedan) class in the Pacific Northwest area.

This was the procedure I used.

On the second Gen pinion shaft I took a grinder to remove the case harden pinion gear to the point of leaving about a 1/8 of an inch of material extra for final machining. On this shaft record the overall length so that when you put the Gen one gear on the end it will be with in .005” to .010”.

On the end of the Gen one pinion gear (Gear End) you will machine in from the end in to the center of the shaft a taper of 6 degrees. You will continue far enough in so that as you work your way outward from the inside you will cause the Gen one pinion gear to fall off. There will be a coarse edge were it separates, debure it by using an air die grinder flapper wheel, 120 grid is fine. At this point do not change the angle on the lathe because you will now put the preground Gen two shaft in the chuck and machine the out side to match the pinion gear ID angle you just separated. The trick here is to remove the material slowly and keep checking the overall length by sliding the Gen one pinion gear on to the Gen two shaft. What you want is an overall length .015” to long with a hand fit. At that point STOP. Now put a small 45 deg. Taper on the end of the shaft and a 3/16 hole ½ “in. This will accommodate the last step of Tig welding.

Take the pinion shaft and put it into a freezer for two hours. Take the Gen one pinion gear and put it in a toaster oven and set to 450 Deg. For 45 minutes. Hold the frozen shaft in a strong vice so that you can drop the heated gear on to the shaft and drive it down with a 2 lb hammer and a large 2 inch brass drift. Be sure that the gear is seated on to the shaft.

Let it cool to the touch the put it back in to the lathe and check it for run out. If you have a good lathe and proper tool bits you will have only .0010” of total run out. That is good and will not present a problem. In most cases it will come from your old Gen two shaft being off to start with.

The last step is to make a container to hold the shaft in water so the gear is sticking out on the top buy 1/8”. This is so that as you Tig weld you do not soften the Gen one gear with the transfer of heat. Also remember the hole on the end. This is so you can put a small bolt in to hook up your ground for welding. You do not want to have arc transfer between the shaft and your water container that will create pits in your final product.

If you are capable of performing this procedure then you will not have any problem with assembly.

Happy Racing, Good Luck
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Old 04-15-07, 09:10 PM
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Wow, I didn't expect to actually see someone do it themselves especially homebrew style. That is awesome though and I commend and thank you for doing that. I won't be doing it myself though...I do everything else but I have no real knowledge (nor am I comfortable) with this.

Keep your eyes out guys if you find one let me know please

K
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