Changing to 4.88 Ring & Pinion gears ?
 

I want to change for higher gear ratio on my N/A race car(s).

So I started reading a little bit here.
Most treats are 'very' old, so I think it would be interesting to renew the discussion, just to sure of what I should do.

It seems as 4.875 (aka 4.88, rounded) is great for track race application.

As her in Luxembourg even in Europe it is difficult to get good and sheep RX7 parts, I have to buy allot of parts in USA and England.
That's why I spent most of my money on shipping :)

So here are some of my questions:
Where can I get one or even two of these 4.88 Ring & Pinion or even a whole LSD for a good price?
Does someone of you guys have one to sell?
Is there a better setup, not too expensive?

Thanks for any suggestions.

Racing Beat, and perhaps MazdaTrix sell both the 4.44 and 4.88 gear sets. There is even a 5.12 offered. Used set sets don't come up for sale very often and go quickly when they are offered. Many of the Aussie owners swap out the Toyota Hilux rearends, which I believe is the Aussie version of either the pickup or small van. We don't get the Hilux here.

If we had Ford rearends, gearsets would be around 150 USD instead of 300-400 for the Mazda sets.

4.88 / 5.12 ?
Which one would you think is the best for
4 hour track racing
4 hour auto cross
I use 2 different cars, one for each application.

Another problem is, that don't want to (can't) spend 300-400 USD plus shipping for this thing.

Hope to find one cheaper.
Is there nobody who stopped or wants to stop racing? :)

Why not go with a Kia Sportage 4X4 ring and pinion (front axle only), which is a 4.778 ratio and will fit perfectly into your 3rd member? You could also consider a ring and pinion from a 87-88 Mazda pick-up (B-xx00----front axle only), which has a 4.44 ratio-----still would scream.

Mike

Sorry,
My English is so good.
http://www.drivetrainspecialists.com...es/3rd-member/
Just to be sure. This whole thing is called 3rd-member?

I found some Kia Sportage rear differentials (4.94) at e-bay but no front ones, and they are expensive.

You will probably get a better answer to your question about gears in the Race Car Tech section. It will also help if you provide details about the track, speeds run, engine configuration, tire sizes, etc..

Love the flames, makes for a good feet and hand warmer, lol.

Here some additional information:

4 hour track races:
The tracks are normally 2-5 km long.
With my actual configuration, 3.9 gear ratio and original transmission, I use mainly the second gear.
I'm driving on slicks front 185 - 215 and rear 250 - 285 on 15" Wheels.
For the next season I planed to install a bridge ported engine with a Weber 48 IDA carburettor.

4 hour auto cross races:
For auto cross I use an original engine with a modified carburettor and straight trough exhaust system.

here ya go these should get you started

https://www.rx7club.com/1st-gen-archive-71/drivetrain-end-all-kia-gear-threads-pics-667307/

https://www.rx7club.com/1st-gen-archive-71/drivetrain-miata-diff-interchange-into-84-85-models-695127/page2/

Thank you for these great links, this will help me.

I didn't find them by myself as I did the wrong searches due to my bad (technical) English.

It is all a bit confusing, but I think I found out, what I need/want.

A front diff/3rd member (4.78) from a 4X4 KIA Sportage

Here in Europe you will not find GLS-SE’s, I think they have never been sold here (not sure about that).
But I’ve never seen a first generation RX7 with a original LSD or a 13B engine here in Europe.
Our 84-85 models also have big axles but no LSD and always 12A engines.

As I have a LSD for big axles and also one for small axles, both come from the USA (e-bay),
I only need the ring and the pinion.

The LSD’s are for my track race cars.
For auto cross I use a 100% locked differential.

As around me there are no places where I could get these 7” rings and pinions, I’ll have to look at e-bay again.

Does someone know where to get them for cheep or does anyone have some for sale?
A whole (open) differential 4.78 that I’ll lock by myself for auto cross would be great too.

If I keep my 3rd member I only have to get the ring and pinion. Is that correct?

Does someone have a list (or know a link) of other cars, models and years which have ring and pinion that fits first generation RX7?

Tomasoft,

The 3rd member is a phrase used to describe the the entire center section of the rear. It comes out as one unit which houses the limited slip clutches and ring and pinion gears, etc. So if you keep your third member, you can swap out just the ring and pinion gears and be done with it. There are other interchangeable gears from other vehicles that will work with your 3rd member, but they do not have the gears that you are looking for. For instance, the gears from a 94-97 Miata are a perfect swap with a GSL-SE, but the gear ratio is a 4:10:1, which is not what you are looking for, if I understand you correctly. I am attaching a parts interchange list for you to look at. Save this list to your hard drive for future reference. Hope this helps.

Mike

http://mrmazda.no-ip.com/interchange.html

Thanks Mike,

This helps me allot.
Also for some other questions I had, e.g. about Flywheels.

Now I just have to find the correct gear and pinions.

Does anyone have an idea?

I found this here: https://www.rx7club.com/showthread.p...on#post5313406

Could someone confirm it?

Yeah, swapping just the R&P will do fine. Im using kia 4.44 Ring and Pinion in my 73 RX-3 (81-82 3rd member) as well as my 84 RX-7. Im also using the 4.78 in my other RX-3. For street use, I like the 4.78 much better than the 4.44.

Thanks for the info.

I think I'll go for the 4.78 on both cars if I'll find one or two.
If I find a cheap 4.44 I'll try it out, It will be better than my 3.9 that I have now.

I'm still searching, .....
It's harder that I thought. :wallbash:
It seems that there are not much old Kia Sportsters here in Europe.

Does anyone have idea?

I finally decided to buy one from Racing Beat, to be sure to have at least one for the beginning of the next season.

http://www.racingbeat.com/resultset....rtNumber=13004
Ring & Pinion Gears 4.875
Retail Price: $415.00

If someone knows a cheaper dealer or a used one, please let me know.
As I need two of them any information is welcome.

Thanks for your help.

Those are nice gears but ouch on the price, especially for the shipping and all. Well, good luck and I hope they work good for you.

Just wanna be sure... Does (B-xx00) mean any B series pickup...???

I don't know shipping fees yet. I contacted Racing Beat only yesterday.

And our customs wants money too :icon_tdow

I’ll keep you informed on price, how they fit (a little bit later) and how they drive (on season 2008).

Does someone know if this will fit my SA2?

Used Differential gearing for Kia SPORTAGE (K00) (10.97-8.03)
The spare part was dismantled from the following vehicle:
Manufacture date: 10/1997
capacity (ccm): 1998
engine performance (KW/PS): 61/83
enginecode: RF

As I'm not allowed to put an e-Bay link on this page, please use this to find it:
Kia SPORTAGE K00 Ausgleichsgetriebe Differential

Thanks for any helpful information.

Here is the picture of the KIA differential mentioned above:
http://www.bilder.gebrauchtteile24.d...45_200x100.jpg

Does someone know if it will fit my SA2?

You best off if you just use the ring and pinion out of the kia. If you are asking if you can bolt in the whole set up pictured above, the answer is definitely not. You can use the carrier with the gears on it but the kia carrier is open not a lsd.

No,
I never wanted to bolt the whole thing into my RX7. :uh:

Just the 3rd member welted for 100% lock into my Auto Cross car.
Or only the ring and pinion with my LSD into my race car.

But the seller cannot (or don’t want to) tell me if it is 4,44 or 4,78.

That's why I ask here if someone knows the answer.

So if I understand you well, this thing should work?
But is it 4,44 or 4,78?

IIRC if it is the front diff it will be 4,78 or 4,88. I do know the front diff is a higher ratio than the rear.