miata 5sp internals in fc 5sp

[fc nut]

I've read a couple of threads that say that they are a direct swap, is this true? Racing Beat says that the input shaft can be swaped(with the proper maching). Can you swap the internals from a miata trans in an fc trans? The reason I'm wondering is, my trans is grinding and I'm looking for an alternative to a rebuild. Thanks. Bryan

[My5ABaby]

From rx7club.com and user RXgirl7

for those of you who know me, i have been thinking about putting a miata transmission into my 89 GTU. i know this swap is common on race cars, but i have never heared of it being done on a daily driven car before(i serched, but i may have missed something). my car has a bone stock S5 motor(22k miles, running strong)and a stock exhaust system. i chose the miatabox because the gears are closer.
i picked up the transmission for $125, used from japan in excelent condition. no gears or synchros had to be replaced.
i decided to go with a racingbeat race pressure plate, and a racingbeat aluminium flywheel. i also installed a competition tranny mount at the same time. i am also running NEO synthetic 75w-90 in the new transmission. installation was done by John at Mazdatrix(thank you!)and the transmission was done by Brian Fields(thanks!)located right behind Mazdatrix.
in order to install the miatabox in an FC, the imput shaft has to be modified by a machinist, and the miata gears need to be inserted into an FC case.
the miata transmission has a very tall first gear, and it was assumed that driving the car on the street in stop and go traffic would be tricky. as soon as i drove the car around the block, all my apprehensions dissapeared. it is extreamly easy to drive the car, starts and hills feel about the same as they did with the stock setup. driving the car around town is a blast. it revs up quickly due to the flywheel, and i can ACCELERATE in 5th gear!
i took the car to Streets of Willow on saturday, and it was absoloutly a blast to drive. i have driven on that track before with my stock transmission, and the difference was quite noticable. 2nd and 3rd gear are much closer, and the car feels more spirited, zippy, and responsive than ever before.
top end in 5th gear is somewhat reduced(155mph @7500rpm)but 5th gear feels much stronger and more responsive. i would say it feels sort of like a 4th gear.
i had a Mazdatrix short shifter installed on my stock tranny, and it was quiet as a mouse. after we installed it on the new tranny, it rattles like a mofo, which has lead us to conclude that shifter rattle is specific to each transmission. more on this topic can be found on the Mazdatrix website.
everyone who has driven the car has given me positive feedback, and the car is an absoloute BLAST to drive. the results completly exceeded my expectations. in my opinion, there is absoloutly no downside to this swap. i would definatly reccomend this swap to almost anyone with an FC. the transmission has completly woken up my motor.

[Rogue_Wulff]

It has been my understanding that Miata 5spd internals are a direct swap into a FB/FC N/A trans case, other than the minor machining required for the input shaft.
Mazda Motorsports sells a custom gearset for both the Miata and RX7 trans. They list the input shafts seperately, but the rest of the gearset is the same for either application.

[killahrx7]

why not just buy another used transmission? i'm sure you would still come out cheaper.

[TitaniumTT]

In talking with Dave @ KDR, certain miata trans can be installed in the FC by simply swapping the bellhousings and sometimes modifiing the input shaft slightly. Give him a call, he may have the parts inhand to build you a trans and get it shipped right to you.

[Black91n/a]

AFAIK it's any of the 5 speeds, but the 1.8 transmissions had better synchros than the 1.6 ones. The input shaft needs to be shortened.
http://www.mazdatrix.com/FAQ/MIATAINPUTSHAFT.HTM

[Whizbang]

In talking with Dave @ KDR, certain miata trans can be installed in the FC by simply swapping the bellhousings and sometimes modifiing the input shaft slightly. Give him a call, he may have the parts inhand to build you a trans and get it shipped right to you.

not sure how you swap the bellhousing on the smooth case transmissions.

[TitaniumTT]

Apparently it can be done with certain models. Otherwise its the internals that need to be swapped

[Max777]

I was looking at this, do you think that the Miata stuff will handle any drifting? or stupid driving for that matter? N/A transmissions are known for being a bit weak even in good condition, or so I heard...

[Black91n/a]

It's not so much swapping bellhousings or anything like that, but more like swapping the Miata guts (contained in the center section), into an FC transmission case. The Miata gearbox is basically the same as the FC NA unit, I wouldn't expect it to be much, if any more durable. They are a known weak point on turbo Miatas (they're lighter, so can take more power to break them).

[Kentetsu]

One trick to aid grinding synchros, which we have had quite a bit of success with, is to use a 50/50 mix of gear lube and ATF. The ATF has plenty of lube, but also has a butt load of detergents which really clean the synchros up and usually gets them working again. This might be worth a shot before seeking a new tranny...

.

[Black91n/a]

ATF is way thinner, that doesn't seem like such a good idea. Redline MT-90 or MTL would probably be a better way to go. I use MT-90 and it's been good to me.

[TitaniumTT]

Don't use Royal Purple with an old tranny. The synthetic base that they use messes with the sync's.

Redline's doesn't. At least this is what I've experienced. Also, I wouldn't use ATF BECUASE of the cleaning properties it has. Instead I would use a 50/50 or 70/30 mix of tranny to 10W-30. I did this in my N/A trans during the winter months MANY moons ago when I was too cheap to sport for the Redline. Now it's redline in EVERY gearbox I own. It even cured the dreaded 2nd gear grind in my Aisin AX-15 in my Jeep despite how cold it gets in the winter.

[Whizbang]

i always remember my jetta i had grinding like crazy in the winter time...Rx7 never has really.

Then again i have issues with reverse just not working. Impossible to get into. Not sure what that is about.

[TitaniumTT]

No reverse sync? Every so often my truck will do that and I'll have to put it into neutral, engage then release the clutch to spin the gears and it usually goes right in.

On a different note - my new 6-spd tranny got here today. Something to think about. If a company can get away with building a transmission in three sections, then mixing and matching sections to fit it into an exponential amount of cars, why wouldn't they? Example. Changing a bellhousing allows it to mount to different engines, changing a tailshaft allows different lengths. The bulk of the internal parts are all the same so it makes sense that interchangabilty would be pretty strait forward. Jeep guys have been doing it for a LONG time.

[Kentetsu]

Using a mix of ATF is an old trick that was made popular by the Datsun racing teams. I've been using it for years with success. As the synchros get gummed up with crud, they stop working. The ATF cleans them out and allows them to start doing their job again.

Can't get into reverse: Yes, this is because there is no synchro for reverse. The recommended method for shifting into reverse is:

Put the clutch in
Move shift lever into 1st gear
Move shift lever into reverse gear
Release clutch

Hope this helps. :)

[fc nut]

sorry it's been awhile since i've been on here. thanks for the input. the trans i got from a friend wasn't gummed up,it was clean.my problem is, i used lucas gear oil in it and that was a mistake. do not use this gear oil. under spirited driving i can't speed shift to the next gear,or they grind.i also am having trouble getting it in gear somtimes.the trans was fine until i had to drive it on a daily basis. i'm going to change the oil tomarrow and see if there is a difference. i will be looking into finding me a miata trans & lsd. the trans internal swap i will be doing, i hate my 5th gear.

[Max777]

lucas oil, really? What's wrong with it? I was considering getting some.

I know the additive is shit in a bottle, but why is their gear oil bad?

EDIT: or is it the same stuff?

[Phoenix7]

so, is there an actual benefit to this amount of tranny work?

[Whizbang]

so i was looking further into this and i have some comparisons. Ill be adding some information to the FAQ.

These are based based on a 9000 rpm shift with 4.78 final drive (personal setup). For the miata vs the FB gearboxes, the 1 - 2 shift is almost equal. But you do see improvement for the 2-3 and the 3-4 shifts.

http://img.photobucket.com/albums/v230/Tsunami_Bomb/Trans%20Diff%20FAQ/miatavs12a.jpg


Now the FC3S Type M transmission sees some improvement for all gears.

http://img.photobucket.com/albums/v230/Tsunami_Bomb/Trans%20Diff%20FAQ/FCvsMiata.jpg


Which leads me to think that there could be benefits to running a 12a transmission if your on a budget, but certainly the full miata transmission is a good route to go. Im have considered using the the miata gears behind the PP but the Mazda box is of a weaker design than say, the T-5. NOW, other options that i am tempted to try involve the use of said T-5. A richmond gear T-5 can come in gears ratios that can keep the engine even higher in the rpms, but until i get an engine built and dynoed, i wont know what ratios i truly want. In the meantime the standard World Class 3.35 transmission is a close enough for me and has a good 5th gear pair for my final drive gearing for tooling around. The rally car might receive something far more drastic like a 5th gear 1:1.

Below is the miata vs. the Ford 3.35 WC T5

http://img.photobucket.com/albums/v230/Tsunami_Bomb/Trans%20Diff%20FAQ/MiatavsT5WC.jpg

[TitaniumTT]

Have you considered the Aisan RY gearbox? Available on the RX8? I haven't directly compared that box to the miata or the n/a S4/5 box but I can tell you it is a DRASTIC improvement (on paper anyway) to the Type-R box. The don't fail from torque either. As just about any RX8 owner what he was doing when he's tranny exploded and you'll soon realize unlike most people that like to parrot missinformation across the internet that it's not torque that kills this trans, it's something far different.

I've dissasembled that trans and have seen it happen first hand. It's interesting for sure but can easily be prevented. Either way, it'll bolt right up to your 13B and if it's in a race car, than shifter placement is of no real concern to you like it is to me which is why it's taken me so friggen long to deal with this box...... I've said too much :suspect:

[Whizbang]

i would consider it if they were cheaper. I want to have the backing of a T5 due to price and the silly amount of after market for it. I can find a T-5 from a wide range of chassis from Nissans, Fords, GM etc or go aftermarket and get any gear ratio i please. For the rally project, i also want a transmission that can handle the the harsh driving style.

i think i have the ratios for the rx8 box, ill make a chart right quick.

[Whizbang]

whammy, yup, id say i see potential there.

http://img.photobucket.com/albums/v230/Tsunami_Bomb/Trans%20Diff%20FAQ/rx8vsmiata.jpg

[TitaniumTT]

Ill be able to give you a better understanding of whether or not it can handle the harsh driving style in the spring. I plan on having it re-rebuilt with new sync's and everything cryo treated as well. I would bet that it'll be able to handle the abuse just fine. I know that 7's only was using them on thier p-port full blown race cars for quite sometime with alot of sucess. They recently went to jerico though. I was a little dissappointed to hear that.

The ratio's are beautiful though, aren't they. I can't wait till spring :D

[Whizbang]

that they are! if i find a good deal, i might have to roll with it for the street car.

need to find one that isnt 1200 dollars

[TitaniumTT]

Find one that's blown for $250 delivered like I did :D

Expect to spent ~$700 on a rebuild and cryo. I know a guy in PA :rofl::suspect:

[Whizbang]

i can rebuild it myself, and ill probably not cryo treat it. Maybe ill pop it in the freezer for a novelty photo. Hmm. blow is a good idea.

[TitaniumTT]

The "blown" one I have is completely reuseable. Basically there's shit inside them that falls apart from over-exentsion. Easy fix, not repair mind you, but fix. PM me if you want more details. I'm keeping this proprietary

[Whizbang]

fine with me. ill see what i come across and ill get back to you about it.

[fc nut]

so, a 12a trans internals will work or do you mean just bolt the trans to my engine? i didn't know they were interchangeable. do i need the driveshaft as well?

[Black91n/a]

so, a 12a trans internals will work or do you mean just bolt the trans to my engine? i didn't know they were interchangeable. do i need the driveshaft as well?

You need to change the tail shaft housing so that the trans will bolt to the crossmember and so that the shifter is in the same place. You can also change the front section, but I don't think it's required.

[fc nut]

which year would be a good strong 12A trans? what about the GSL SE trans?

[Black91n/a]

I'd pick the one with the best gearing, but if there's a difference in strength, the later one's are probably slightly preferable.

[Whizbang]

which year would be a good strong 12A trans? what about the GSL SE trans?

gslse transmission has no real differences as far as strength is concerned.

Just a different fifth gear. (these are for 84-85)

12a 5th: 0.758

13b 5th: 0.807

[fc nut]

i want a 5th gear that my car doesn't fall on it's face after i run 4th gear out.

[TitaniumTT]

Isn't that the point of an OVERDRIVE?

Buy a J-Spec S5 TII trans - .84 overdrive. Personally I'd rather have something in the low .7's for my car, get a little better highway mpg's

[fc nut]

i don't care too much for OD.the problem i have and any other n/a car, after i shift at 120 from 4th it barely accelerates. i want it to keep accelerating if i want it to.

[TitaniumTT]

make more hp or change the final drive ratio

[fc nut]

true. i need to replace my trany anyway. power is on my to do list.

[fc nut]

well,i picked up another stock s4 trans yesterday. the price was right $50,so we'll see how it works. if it doesn't,i'll get a 12a trans.