MOD EDIT: Lots of info in this thread.....but the KIA R and P doesnt work in the RX8.

I've been hunting for a 4.778 and think I found a great solution for $295. First, check this S2000 video out. It shows what a ring and pinion swap from the stock S2000 4.10 gear to 4.57 gear can do.

Click HERE to see video of a stock S2k vs S2k w/4.57 gears

Apparently from the S2000 forum, the RX-8 stock 4.444 ring and pinion and the aftermarket Mazda 4.778 will fit in the S2000. http://www.s2ki.com/forums/index.php...ic=182172&st=0

For more proof, check out what our MX-5 brother has also concluded, Miata Drivetrain Interchange Guide

Also, it seems Mazda has been parting out its gears to Honda S2000s and Kia Sportages 4X4 1994-2002. The front axle of the Kia Sportage has the Mazda 4.778 ring and pinion. The S2000 guys are putting in the stock RX-8 4.444 and the Sportage 4.778. You can order it from www.kiaparts.com Part# MM057-27-110 for $295.62+s/h.

Even more interesting, it seems awfully coincidental that there is a Mazmart 4.10 Differential Swap ( S2000) , https://www.rx8club.com/showthread.php?t=76673&highlight=4.10

Last, if you want the 5.125 gearing, all you have to do is the 4.778 swap and step down to 225/40/18, and you'll be real close to that. This with the flywheel, CZ, High Flow Cat, and REVi will put us well into EVO, WRX STi and 350Z territory.

NOTE: You can use a Yellow Box $90+s/h to correct your speedo and odometer easily. Your city gas mileage will really improve with the swap, as will 0-60mph and 1/4mi. I estimate a 300-600rpm change at speed, if your worried about this just drive slower... 75 instead of 82mph.

 

Damn that is pretty affordable, and would probably kick *** on the track.

Just read through some more of the s2k thread and it looks like the Kia 4.77 gear might be a bit weak, and some people are Cryo treating them to help out. These are the same people that do Frozen Rotors: http://www.diversifiedcryogenics.com...rtspricing.htm

 

It always seemed a little suspicious to me, with the similar final drive ratios between makes out of Asia. That 4.10 swap immediately made me think of the S2000 as well. Will that Yellow Box work on the 8? Where does it hook up?

4.78 sounds good to me. I need to slow down on the highway anyway . I'm gonna get burned by the coppers sooner or later. Given the 4spd's crappy gear ratios, this might be nice.

 

Yes, this is all true!, I did not know that we can use the same gears though from the s2k, hmm! thats great that it's such a affordable price to!






My cousin has an S2000 and he will be getting his 4.57 Gears very soon, If you watch the video you can really tell differnce. well all i can say is For that price? PUT ME ON THE LIST ASAP

 

Here are some 4.777's

https://www.rx8club.com/series-i-aftermarket-performance-modifications-23/mi-new-parts-77052/

 

You might even be able to sell your stock RX-8 4.444 to an S2000 owner!

The S2000 choice alternative is the 4.57 aftermarket gear which is very very noisy, however strong but not a precision high quality unit like Mazda's 4.444. Not a noticeable difference between the two in performance. I suspect the 4.444 were scarce since the RX-8 was into later production hence the 4.57 alternative.

The 4.778 option on the S2000 is a bit too much on the highway for most drivers, 5200rpm+ at 75-80mph.

 

Only real question is how much to install. I'm an avid do it yourselfer but I just looked at the shop manual for the Diff and there are a crapload of parts, and they look like they all have to fit perfectly or your screwed.

 

Yellow Box installs like this:



Rick has them for $90+s/h, http://www.ricks2k.com/products/yellowbox.php

 

I knew somone would find a cheap alternative if they did a bit of research. Excellent find!

 

indeed good find......but that would be one loud ride on teh highway to see my gf at 5200 rpm .....awe well guess it's a give and take kinda thing

edit: just noiced that was for the s2000 drivers on the highway..i wonder what our rpm's would be at at 75 in 6th with the new gearing....hmm time to do some research i guess.

 

You can also use the Speedo Healer to recalibrate your speedometer and odometer...

 

Based on this attachment, which may not be entirely accurate as it is theoretical rpm vs mph, at 83mph your at 4000 rpm stock and just above 4300 with the 4.778 gear. Regardless, take your cruising rpm and multiply it by 1.076 and you'll have your new rpm.

 

Speed vs RPM for the 4.444 gear


Speed vs RPM for the 4.778 gear


Speed vs RPM for the 4.778 gear and 225/40/18 (5.125 equivalent gear)

 

Thats slick~
________
CHILD WELLBUTRIN

 

you might have your labels for those charts reversed

:D

 

sweet find! now for someone to go do it

 

Gotta hoist the flag to the top of the mast on the "you'll get better gas mileage with a numerically higher rear axle ratio" bit.

I can't say a priori that a silly high gear won't put an 8 into the same league as an STi or Evo. Common sense says, from 0-60, maybe, 1/4 mile, I frickin' doubt it.

Also, 1st gear will become pretty much useless with a 5.x gear, don't you think?

It will be cool to see how this stuff works out when people try it.

 

Makes perfect common sense if you had some .

The shorter final gear will make the greatest impact on 1st gear, then 2nd less so, 3rd even less so, and so on... The reverse happens in the upper gears where this mechanical advantage is lost to higher RPMs in 4th, more in 5th and even more in 6th. That's why city driving will benefit from the lower gears. It's really pretty simple,

Shorter gearing = a mechanical advantage = less work = better mpg

Analogy: Try riding around in a 10 speed bicycle in the lowest gear at a slow speed. This may be difficult since you would have to put in more work. Now do the same in a highest gear yet still riding at a slow speed, less work right. That's why city driving will benefit from the lower gears.

Now do the opposite. Try riding around in the lowest gear at a very high speed, a lot less work than riding around in the highest gear at a high speed. You will gain mpg in city driving, but will lose mpg on the highway. However, you can compensate for the loss of mpg at highspeed by driving a little slower on the highway. The spread between the 4.444 and 4.778 gear is about 7mph (300-600rpm) at around 70-80mph.

Last, an even simpler concept, a quicker 0-60mph = a quicker 1/4mi .

However your version of "common sense" says a quicker 0-60mph = the same 1/4mi time

 

Here are the old vs new mph vs rpm. Looks like you would probably get same or better mph below 55mph.

 

I dont understand those figures for the current ratio. 132 in 4th gear is unattainable for our current setup. From my experience.. 4th at 9000 rpm is 120. 132 isnt correct.

 

those r simply theoretical rpm vs mph, theres drivetrain loss and air resistance involved in reality, but its a good comparsion of how ur rpm would change when u change out the final drive
________
BUBBLERS

 

^The only way those numbers are wrong is if the Formula's are wrong. There should be no drivetrain/air resistance factored into that unless you clutch is slipping.

 

Canzoomer did this with 215/35/17 Nokian WR tires that have a 5% shorter drive ratio with no clutch drop... "Slipped clutch slightly, at launch, and at 1st/2nd shift up to 4500rpm" The 35s are equivalent to a 4.778 gear.

With the the 4.778 gear and 225/40/18, you should improve the 1/4mi since this combo makes a 5.125 gear equivalent.

 

Hmm okay, so now we've found other cars that share the same rear gear as our car. Now let's find another car that shares our Aisin transmission, but with taller 5th and 6th gears. The 4th to 5th and 5th to 6th shifts give a meager 500 RPM drop each. What's the point of a 6-speed if three of your ratios are crammed so close together?

 

I would definitely be with a taller 6th.