As the title says will the synchros of this gear-set be able to fit in an na transmission? I know you guys are probably thinking that it's a waste of time of time to do on an na 6-port motor. Although, I'm using this car as a daily for right now but It would be nice to have an overall wider power band for the spirited driving on the canyons and of course on the small tracks with little to no straightaways.

I'm asking since I have an extra TII driveshaft and was debating whether I would sell it or not.

To keep this short, do I have to buy a TII transmission to be able to fit this gear-set? If so, then damn. Up up and away it goes to the for sale section.

 

TII gears are way different than n/a. not that i have tried, but i realllllllly doubt the synchros are similar otherwise the rebuild kits wouldn't be $$$$ for the turbo compared to the non turbo. not that i'm quite getting what you're asking anyways since syncros have nothing to do with gear ratios, that is the gear's job and no, the mainshafts will not swap between n/a and TII.

 

Ah okay thanks for the clarifications. By main shaft are you referring to the input shaft correct? I didn't realize that obviously the n/a and tii input shaft are different diameter sizes. *facepalm*

 

everything is different short of the pilot diameter. by mainshaft i mean the whole main from input to output including the cluster gears and countershaft. but yes, quick example is the spline size and count of the TII versus n/a since they use different clutch sets.

miata gears are your only alternatives that i know of for an n/a box.


for the turbo transmissions, i haven't researched it but the TII shares the same case as the B2600 series pickups, which may have a shorter spread than the cars. i don't know if they offset it by simply gearing the diff or put a different gearset in those trannies. with the 4.10 diff ratio in the cars they have a possible top speed of around 180mph, the trucks require torque so they would either have shorter gears or a significantly more geared diff, possibly both. i do know the TII shares the same synchros with the B2600 but that does not necessarily mean the gearing is the same.

 

the B2600 uses a wider spread, so 1st is a granny gear, 4th is straight through, and it uses the JDM FD 5th gear, .825. it may share the main shaft, bearings and synchros, but everything else is different. it uses a 3.9 diff, that is NOT common with any other Mazda, and i think it came on 14" wheels, so at 80mph, its turning like 4000rpm.

 

well then, i guess my AWD super7 project may just have to start out in 2nd gear instead of 1st...

 

Thanks man! I would look into more of that B2600 but from what I was told recently the bellhousing of the Tii tranny don't line up with the n/a. Which was what I heard ages ago prior to me asking this question but ah well.

I also need to research more on the gearing-ratios. Either way thanks again!

 

the n/a transmission bellhousing is molded into the case so no it cannot be interchanged, the bellhousing to block bolt pattern is the same between n/a and TII so the TII is a direct fit onto an n/a engine. but the flywheel would need to be changed to accomodate the larger clutch, as well as the slave, starter and adapt the driveshaft.

the n/a has much softer shifting but it is a glass tranny, does not like to be abused or raced.


if you really want a close ratio set you could try to adapt an RX8 6 speed manual transmission however the same as above applies. you would need a Turbo clutch+flywheel, RX8 starter, a custom TII to n/a driveshaft with length modified since the 8 tranny is a unique length and a custom transmission mount bracket since the RX8 uses an FD type torque brace mount. in all honesty though, you can pick up a RX8 6 speed for about $200-250 so the initial cost isn't really that steep. keep in mind the 6 speed is only a hair more stout than the n/a 5 speed and is still miles from the TII for durability. the RX8 trannies are also throwaway units, even a basic synchro and bearing set alone is $750, once you start replacing gears it gets into the thousands to rebuild but they are not hard to find in used but working condition.

 

Thanks so much! I'll consider these options

 

Isn't the shifter location a problem with the RX8 tranny in the FC?

 

I know of one that is used in REW FC with over 400 to the wheels. After a missed shift on a race track did it start to go. Think 30 or 40k total. Mounting took a bit, like noted earlier. But it fits just fine in th FC

 

IIRC it 3" shorter or at least the shifter position is so it ends up in the stereo. I know one guy on here relocated the shifter and another moved the whole engine back. Yet another was in a race car so it didn't matter. The other issue is there is no provision for a speedometer as the Rx8 used one of the ABS wheel speed sensors for the speedo IIRC.

 

you talkin about me?

yeah i moved it back, whats it too ya.. i also used the original auto drive shaft UNMODIFIED.. everyone seems to miss this bit tho. like all my parts are factory, save the honda slave cylinder.

 

i beleive the miata 6 speed tail housing has speedometer and can be swapped onto the rx8 trans... or u can get the miata 6 speed and swap the rx8 bellhousing(not confirmed on the last one)

either way i found this info and made a note when it times come for me to care about not having a speedometer again. it may be some time...

 

I too will make a note of this as I'd like to swap a Rx8 trans in one day and a speedometer would be nice. I have my own ideas about moving the shifter.

 

the RX8 bellhousing is part of the transmission, similar to the non turbo FC. least i am almost certain of it, aint going outside at midnight to check, heh.

 

I believe their are 2 if not 3 different style transmission with one of them having a removable bell housing . Earliest if I remember correctly. The later years receive a Aisin transmission that did not have a removable bell housing. But not 100% on this it been a while since I've worked on 8's

 

the S1 is an Aisin, the later models were made by mazda.

edit: the Aisin does appear to have a removable bellhousing so i remembered wrong anyhow.

 

i'm not sure about that, i've had both in my hands and the miata version uses different sized shafts (the miata is like an NA FC size, and the Rx8 is bigger than a turbo). that being said i think the bellhousing will swap, it uses the same bearing. i think the tail wont, as the output shaft is bigger on the Rx8, and in any case the Rx8 tail shaft has no place to put the speedo gear, although that would be pretty simple