Hello,

Does anyone have a 5.12 or 4.88 ring and pinion set for sale or know of anyone building these now?

Thanks

Tom

 

For an fc?

Non-turbo I assume?

 

Yes, preferably a FC non-turbo.

I could swap over to a turbo drivetrain if need be but I haven't seen any turbo 4.88 or 5.12 gears.

 

If you can live with a 4.77 -> 86-95 Ring & Pinions, Bearings, and Seals

 

I've spoken to Dave Lemon over at Mazdatrix, its a good option but slow turnaround time because they are all custom made. I would still prefer a 5.12 or 4.88.

 

I have a ronin speedworks ford 8.8 IRS in my car. lots of cheap gear choices. 5.14s are $200-300

FC Ford 8.8 IRS Mounting Kit

 

yes on the ford...i have the ford 7.5 i.r.s and just put gears in it last month. $189 for 456 gears from summit racing,the 8.8 is more popular but the 7.5 only set me back $75 an salvage yard. the 7.5 and the 8.8 use the same ring an pinion gear as the mustang streight axel as well as the ford ranger,thats why there so much cheper!

 

I wonder if the series 2 RX-8 gearset (4.78) fits in a Turbo II rearend. I know little of RX-8 swappery.

After going to 4.78 and better tires, I'm snapping axles in the splines, so I did an end run around the problem and went to a Ford 9". 8.8 is almost as beefy but you can't get as many good diffs for the 8.8. Or at least not cheaply. NASCAR takeout Lockers are like $200-300 on eBay, spools are cheap too. The 8.8 has... a Ford Motorsport Torsen that you can sometimes find on eBay for $200-300 new if you are patient. If you like Torsens. The Traction-Lok for the 8.8 is a complete turd though.

 

The ford IRS seems crazy stout and fairly cheap. Unfortunately it would probably kick me into a much higher class level... I know Mike Van Steinberg at ISC can get the 4.88s but its $$$ and takes 6 months. Spoke with Dave Lemon at Mazdatrix and it a long lead time on his 4.77s also. Guess we won't have them for the 14hours of Daytona coming up.

 

RX8 ring a pinions fit in FD "short pinion" diffs... but not in TIIs with long pinions.

The 4.88s and 5.12s are similar and need to be made with TII cores to lengthen the pinion...

 

Those are the T2 Torsens and have the lower bias ratios Those came in some Ford Rangers. They are OK but a Torsen T2R or even a Detroit Truetrac both have more bias ratio.

The 9" is also heavier and less efficient. You can get just as many good diffs for the 8.8, they just are not Nascar or drag race takeout stuff. You can minispool an open 8.8 diff for pretty cheap.

 

I see the 9 inch's higher pinion offset as a benefit, not a downside. It allows the rearend to be set higher in the chassis, or in the case of a solid axle it allows more suspension travel. In a 1st-gen the first limiting factor for travel is the driveshaft hitting the floor right under the rear seat/bins crossmember, which is tricky to alter to say the least.

Of course, there are junkyardable 8.8 IRS diffs available. There are 9" based IRS diffs available, either as DIY parts or as prefab assemblies, but for nowhere near as inexpensive as calling up LKQ and giving them a delivery address and a credit card number.

 

Speedsource used to make 4.88 and the same with ISC racing.

Welcome to Rebello Racing and Mazdatrix can do the fabrication for you.

Rebello costs about $350 + shipping them all the gears to do the modification. I may be doing a spare one here in the future. You'll need a Kia 4.77 r&p set and a long pinion for them to modify.

Good luck!

http://www.rebelloracing.com/

His son does the modification.

 

When comparing the 9 inch to the 8.8 just know the 9" is comparatively heavier. The benefit of the 9" over the 8.8 is the ease of gear ratio changes. If you run different tracks and benefit from rear end ratio changes the 9" makes it easy. To me that's pretty much where the significant benefit ends. Added suspension travel may be a factor for off roading where suspension travel is everything. But not so much on a racetrack.