Gear Swap?
 

Pretty much I don't even need my 5th gear, even on the highway... the gears seems WAY too far apart to me. Can someone point me in the right direction on a gear swap? I searched and didn't find anything useful.

Thanks,
iSP33D-for-J3SUS :bigthumb:

There are several ways of going about this. You can swap in a 4.3:1 ring and pinion from the GTUs. You can swap in a diiferent 5th gear from a different year. You can also do a tranny swap. The case from the SA/FB can bolt between the tailshaft and bellhousing of the FC tranny, and bolt right into the chassis. You can do the same with a 626 RWD tranny too apparently. You can also get a Miata tranny and swap the internals into the FC case with only minor mods. There's other more expensive things too, like getting a 4.7:1 or 5.12:1 rear end, but they're mainly for racing. You could also do some other tranny swap, and there's a few companies that offer dog gear conversions (with much lower, tighter gearing)for the turbo tranny's, but that's expensive $$$$$$$$$$$$$$$$$$$$.

i heard, HEARD that fox mustang tranny internals can fit too

Is it possible to swap a custom 5th gear for lower freeway/cruising RPMs?

lol i know, complete opposite from this thread...but i do A LOT of freeway driving...1000+ miles a week...sometimes it'd be nice to do 90mph at 2k rpm :bigthumb:

J-spec TII tranny's have a shorter 5th gear...

last I knew Tri-point engineering had 4.30 and 4.60 gear sets for $550. Someone on this forum has 4.60 gears in his 2nd.

i swapped in miata gears with EXCELENT results. shorter gears, better acceleration(tall ass 1st tho). i would reccomend it to NA owners. :)

Any more info on this?

And what are the stock N/A 2nd gen (i.e. mine; 1988) gear ratoios compared to the miata ratios, etc?

iSP33D-for-J3SUS:bigthumb:

Your car wont make enough power at 2k rpm to keep it at 90mph

https://www.rx7club.com/showthread.p...ht=miata+gears

has some decent info on RWD 626 gears....

manual tranny with 4.10 rear end:

1st: 3.480:1
2nd: 2.001:1
3rd: 1.370:1
4th: 1.00:1
5th: .697:1

That's the final drive ratio, all gears included.

I'm in the midst of changing the internals of an S4 LSD from an auto GXL into the case of my S4 open diff, with 4.10 gears. I've been doing a bit of research...

James

Isn't that for 81-85's though?

iSP33D-for-J3SUS :bigthumb:

oops, my bad - sorry about that

https://www.rx7club.com/showthread.p...0&page=1&pp=15

^ miata info...

Hey Claire how are you? :)

Ok, 80mph at 2k. thats a grand less than what it does now, and it still makes FINE power even uphill in 5th. I hear a lot of people talk about how they have no power in their 5th gear. idk mine makes plenty! makes enouh that i can go from 80 to 115 without any trouble and it dosnt take long either.

Id imagine that at 90mph if i were at 2k, it would hold it there just fine. maybe not up a hill. but flat to moderate uphills, no problem

I second that, I can accelerate just fine in 5th as well. However apparently the PO had the tranny rebuilt 2 years ago.

I'm interested in this GTUs gear swap... how much of a difference would it actually make? Could I do the work myself with a good tutorial? Also, where would I find the GTUs parts? Junkyard? Or can I buy them from a dealer / online store?

iSP33D-for-J3SUS :bigthumb:

Mazdatrix,Racing Beat, and Rotary Performance all sell the 4.3 gear sets I believe.

went on their site and they only show 4.10 and their email address is not in service. Any other info on this?

Hmmm, that's a very interesting swap. :D Assuming the gears and synchros are in decent shape on the new internals, is this something you could do on your own w/o any real special tools? Do the internals pretty much just drop in the FC case?

the internals pretty much drop into the fc case, excpet you have to have the miata imput shaft re-splined and shortened a bit. the miatabox i bought was in PERFECT shape.
the GTUs rear end is hard to find, i believe theres a used one at mazdatrix now.
i would reccomend the miata swap, but that is my personal opinion. if there is a mazfest again this year, ill be giving rides in the car, for anyone who is interested in checking out the results of the swap :)

I'm kindof suprised noone has mentioned this yet but the S4 turbo transmissions have a shorter 5th and the ratio spacing feels much more natural than the big jump to the NA 5th. I say go S4 T2 trans and rear end and then if you decide for more power later then you have the driveline strength that you will need to handle it. I love the T2 ratios.