miata 5sp internals in fc 5sp

[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.




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




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

[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

[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.

[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

[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

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

[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?