Where to find 2nd Gen RX-7 5.12 diff gear

[Doncan]

<span style="font-family:Times New Roman">Where can I buy 4.88 or 5.12 diff gears for my 2nd gen normally aspirated RX-7 ?? Thanks !!</span>

[ddewhurst]

Do a google search for mazdatrix they have them.

[mbuskuhl]

In my recent research on this topic, Mazda made a 4.30 gear. The 4.88 and 5.12 are custom one off fab&#39;d R&P&#39;s (please correct me if wrong!). Due to the work that goes into them, they take a long time to get, are hard to come by and fetch a good sum of money. ISC Racing has one on it&#39;s site right now ready to go. www.iscracing.net

Mazdatrix goes to a 4.30 is all http://www.mazdatrix.com/g7.htm

[jrx13]

actually, the ring and pinions are from the 1st generation rx-7s. Buy the gear ratio you want from mazda motorsports. Then you send ISC racing your new short pinion with your used long pinion (2nd generation rx-7) and they will machine/graft the end so you end up with a long pinion with a 5.12 or 4.88 ratio.

[mazda49]

What the above responses are saying is true. The 5:12 & 4:88 gears are available from MAZDA Competition
and if you are a registered member (all you have to do is supply a photo of your car and results from two races annually). The pinion gears has to be lengthened. This is done by providing a pinion from a donor
rearend. Since the pinion you purchase with the ring gear new is short (originally, manufactured for a truck or 1st genration car) you have to cut the two at a proper point, machine the two to fit with a tapered female/male press fit beveled edge area at the joint to be welded by an experts, then machined back to tolerance with very minimal run-out. Because of the tedious process and exacting specifications most
machine shops will not do one of&#39;s. Most want a minimum of 5 to to do at one time since the set-up of the
fixture and the jig for one is time consuming.....I have searched at great expense, to find a source to to all of the above and do it with all the expertise of company that builds stock car differentials/rearends. I can get yours done. Call me if you have and interest as I am getting an order up now for the process. You may call me at 843-222-2897. You are not going to find either of these gear ratios in a junk yard or used as they
are special purpose built. I&#39;ve already been through this lots of time and energy.....by the way this is the most reliable performance you can buy.

[ITS51RX7]

I have a 5.12 LSD complete diff that was done by ISC that I will sell if you are interested.
$ 750

[tdw6974]

I have a 5.12 LSD complete diff that was done by ISC that I will sell if you are interested.
$ 750
[/b]
Set PM message. Tom Weaver

[mbuskuhl]

I have a 5.12 LSD complete diff that was done by ISC that I will sell if you are interested.
$ 750
[/b]

Sent PM. I think you should sell it to me first ;)

[dickita15]

Sent PM. I think you should sell it to me first ;)
[/b]
cool a bidding war

[mbuskuhl]

cool a bidding war
[/b]

I&#39;m 3rd in line. Here&#39;s a vote for 24 hr ebay auction on it! If anyone else has one they can part with, no need to post here. Just PM me. :biggrinsanta:

[Andy Bettencourt]

ISC and Speedsource aren&#39;t making any more of these new IIRC. We just had 2 built with a local supplier.

Oh ya, PM sent too. If that&#39;s a Torsen, it ain&#39;t selling for $750.

EDIT: We are out - no torsen.

[ITS51RX7]

Here is some info on the diff for sale.

It is NOT a torsen unit it is the LSD clutch pack version.

It is currently installed in my old 2nd gen that I ran into the wall at IRP last year. All running gear Motor, trans, rear end are fine , but the front frame rails were bent beyond fixing.

I purchased another roller 2nd gen from Chris Ludwig, his car already had a 5.12 rear so I do not need two of these. I swapped the motor and trans over and I am ready to get rid of everything else on the bent car.
I am adding a picture of the car the rear end is still in, I wish it was still in the same condition.

Tom was the first one who wanted this diff, so it is his if everything goes ok.

[Doncan]

Damn !! what about me; the starter of the topic ??? Put me second in line then.... :rolleyes:

[mbuskuhl]

Here is some info on the diff for sale.

It is NOT a torsen unit it is the LSD clutch pack version.

It is currently installed in my old 2nd gen that I ran into the wall at IRP last year. All running gear Motor, trans, rear end are fine , but the front frame rails were bent beyond fixing.

I purchased another roller 2nd gen from Chris Ludwig, his car already had a 5.12 rear so I do not need two of these. I swapped the motor and trans over and I am ready to get rid of everything else on the bent car.
I am adding a picture of the car the rear end is still in, I wish it was still in the same condition.

Tom was the first one who wanted this diff, so it is his if everything goes ok.
[/b]


If Tom falls out, I&#39;m still interested even given this information. Do you know if a guy by the name of Greg Sabol built this diff or do you know who did? Does it have the exrta clutch pack plates and springs from Mazdacomp? - I think it&#39;s 6 vs. 4 from what I&#39;m told. I have another one lined up to buy tomorrow unless this comes through. I sent a PM earlier with my phone, call me if you want to do the deal. Paypal or your preferred payment method ready. :eclipsee_steering:

[Doncan]

<span style="font-family:Times New Roman">In case I want to do the conversion myself, do I need both first gen ring & pinion or do I need only the first gen pinion with the second gen ring ??</span>

[C. Ludwig]

You going to be at IRP Mike? Love to see my old car run. :OLA:

[seckerich]

<span style="font-family:Times New Roman">In case I want to do the conversion myself, do I need both first gen ring & pinion or do I need only the first gen pinion with the second gen ring ??</span>
[/b]
To answer your question--you need to order the complete set from mazda with a matched ring and pinion. You do not want to try this if you have to ask the question. It takes some specialized equipment and fixtures to do it right. If you have never set up a rear gear before I would have that done by someone qualified or you will have some expensive scrap metal after the first race. Not trying to be harsh, just don&#39;t want you to make an expensive mistake.

[ITS51RX7]

The 5.12 was sold and shipped today to Tom Weaver,
Thanks to all that were interested.

Chris, I sent you an e-mail <_<

[Doncan]

To answer your question--you need to order the complete set from mazda with a matched ring and pinion. You do not want to try this if you have to ask the question. It takes some specialized equipment and fixtures to do it right. If you have never set up a rear gear before I would have that done by someone qualified or you will have some expensive scrap metal after the first race. Not trying to be harsh, just don&#39;t want you to make an expensive mistake.
[/b]
Thanks a lot for your respond and advice. Don&#39;t worry because I won&#39;t be doing the job myself. I have the mechanic and the machine shop with the necesary equipment to do the job nicely. I just want to know what is the necessary ring and pinion combo to do the conversion for at least a 4.56 or lower ratio. You said I need to buy both ring and pinion set from a first gen RX-7. Do you know from what year and model ?? My car is street driven but I run actively in time trials events and would love to take advantage from the benefits of lower gears. :eclipsee_steering:

http://www.imagestation.com/picture/sraid223/p0e7bd1b23f14848931e6cad0933137b8/eb0fef00.jpg

[seckerich]

The 4.88 and 5.12 were never in a production model and were sold through Mazdaspeed. They were only made for the early RX7 and other comp vehicles but never for the 2nd gen. Thats why you have to modify them to fit. Options that will fit from cars are a 4.11, 3.9, and a hard to find 4.52. Post on here for a 4.88 if you want a reasonable track gear for the price. Most people started with the 4.88 before we got the 5.12. I sold the last one I had but will see what I can find if you want one.

[ITS51RX7]

Doncan,
Here is the link to the 5.12 r+p
http://www.mazdatrix.com/getprice.asp?partnum=27-1100-1480
You will also need the long pinion from your 2nd gen, because the long pinion and the new 5.12 short pinion will be cut in half and welded back together to make the long nose 5.12 pinion .
While you have it apart, new bearings, disc&#39;s and seals.

Have fun, I know that I would not attempt this procedure.

[Andy Bettencourt]

We just built two from scratch and they cost about $2200 in parts and labor. New guy doing our pinion conversions.

[Doncan]

Guys; thanks A LOT for all of your responses. :023: It&#39;s good to know I can count with your support and read the pro&#39;s and con&#39;s of the conversion. I think I won&#39;t have much problems at all if I make the mod because my RX-7 is normally aspirated and won&#39;t be making more than 210 hp to the wheels (much less the torque) and I never drag race it either, so it should hold on well. I think I will try the 4.875 set so I don&#39;t choke too much my car on the highway because it&#39;s still my daily driver. Also I&#39;ll be running 17 x 8 wheels with 235/45/17 Toyo RA-1 rubber. I just love how my 7&#39;ven runs at the track and if everything goes up well, I&#39;ll be kicking some butt&#39;s this season. So if anybody out there has one in good condition and wish to sell it for a reasonable price, let me now to see what can be arranged. :cavallo:

[mbuskuhl]

Keep an eye out on RX7club.com - that&#39;s where I found mine. It was shipped yesterday via UPS Ground :026:

From an EP guy on that site...

Rear end for FC NA 5.12 gear.
Rear has about 6 events on it. EVERYTHING was new at that point, including bearings, gears and anything that moves. Competition LSD parts. It cost about $2000 to build this way, yours for $1200

[its66]

Another option might be to use a shorter tire. That 17 inch with the 235 will look great, but is a pretty tall combination at about 25.3 inches. The stock tire was almost an inch shorter. If you had a way to run a 15x7 wheel with a 225/50, you could find a 4.30 diff/gear and have almost as much torque multiplication as with the 4.88. Another advantage of this setup would be that the whole car would be an inch closer to the ground without adjusting anything.

Just a different way to accomplish some of the same objectives. If you ended up with a set of 17&#39;s for the street, and a set of 15&#39;s for track days, it might not be cheaper(depending on the wheel choice)

[Doncan]

Another option might be to use a shorter tire. That 17 inch with the 235 will look great, but is a pretty tall combination at about 25.3 inches. The stock tire was almost an inch shorter. If you had a way to run a 15x7 wheel with a 225/50, you could find a 4.30 diff/gear and have almost as much torque multiplication as with the 4.88. Another advantage of this setup would be that the whole car would be an inch closer to the ground without adjusting anything.

Just a different way to accomplish some of the same objectives. If you ended up with a set of 17&#39;s for the street, and a set of 15&#39;s for track days, it might not be cheaper(depending on the wheel choice)
[/b]

<span style="font-family:Times New Roman">Right now I have a set of 15x6 BBS wheels that came OEM in the RX-7 convertible that I bought as my primary option to use with the 225/50/15 RA-1 tires as you mentioned. I&#39;m considering the 17x8 with the 235/45/17 for various reasons; because of the bigger contact patch needed to effectively turn and stop my rather heavy car (around 2,875 with me onboard) and because nowadays it&#39;s easier to find wider wheels and tires for autocross in 17&#39;&#39;. But I&#39;m very awared of the higher center of gravity issue and the heavier rotational mass the car will have to deal with. That&#39;s why I&#39;m looking for the 4.88 or lower gear ratio among other things.</span>