The solution is dependent on the input shaft spline and diameter of the Aisin AZ6 transmission, which is either the same or different than the FB clutch, depending on what part of the thread you read here, it seems. I didn't pursue this because the cost was escalating each time I figured out the next step and I had access to an $80 '84 transmission courtesy of 79+80+84rx7...but here's how it would've gone down if I was willing to spend 3X what I paid for the car in the first place...

• Buy used Aisin AZ6 transmission for $950, shipped to your shop of choice...$1050 if you want a residential delivery.
• Custom mounting plate fabrication, 1" plate....unknown price, guesstimating something in the neighborhood of $500.
• Driveshaft shortened and balanced, $145.
• Custom center console since the shifter position is going to be about 1 - 2" further back...price dependent on materials of choice.

Other than that, it's quite possible.:pat:

Since I have a spare transmission for Furious, I now know I'll never actually be trying this swap....:cool:

But still, $2k is a hell of a lot cheaper than a decent gearset for the 5-speed, if you consider the 6-speed to be a race 5-speed with a useless extralow gear.

I don't know of anybody who still makes gearsets for the smoothcase, but you can get decent-ratioed gears for the Turbo unit for about $5-7k.

not sure if i posted it here or not, but mazda has 3 flavours of this transmission, and then another 6 speed box thats totally different.

the 06 miata has a 6 speed, based off of the P type transmission from the ford trucks, and since theres no rotary bellhousing, this ones a no go

y601: this is the 00-06 miata non turbo 6 speed
y602: this is the mazdaspeed miata trans, its got some hardened parts in it, but basically its not much different
y610: this is the rx8 trans.

the miata's use an NA clutch, the rx8 uses a turbo 2 clutch. the miata uses the NA output shaft, the rx8 uses a turbo style. the rx8 has a rotary bellhousing, which looks like will go onto a miata transsmission. the miata has a spot for a speed sensor/speedo drive, the rx8 does not.

the rx8 has the shifter location where the fd does, or 2" further forward than the 81-92 rx7 transmissions. i dont know about the miata.

if you have a miata, the 6speed except for 1 bolt with the 5 speeds.

the rx8 transmission uses a slightly different starter than a t2, one of the mounting bolts is/are different. also the rx8 uses a weirdo slave cylinder.

so if you're putting an rx8 trans into an fb heres your list of problems/fab items
1. you need a turbo clutch and flywheel
2. turbo style driveshaft
3. shifter moves!
4. you need to fab a trans mount, as the miata and rx8 use power plant frames
5. you no longer have a speedo drive...

miata trans into fb
1. you need the rx8 bellhousing, it looks like it works, but it might not
2. you need a turbo diameter clutch with non turbo clutch splines, i think RB has it
3. shifter might still move, i dunno
4. still need to fab up trans mount

Forgot the trans mount fabrication, so add about $75 to the above total. With the plate, it won't matter what the bell housing pattern is, FB, RX7,8, etc...only the actual width of the housing. Since the Aisin AZ6 transmission was meant to bolt into the 10AE Miatas, the width shouldn't be that much different than the normal Miata transmission or floorpan mods would have had to be part of just the 10AE cars and not the whole car line, an unlikely mass production scenario.

The actual extra length of the Aisin AZ6 transmission input shaft is what makes the plate scenario feasible, it's just a matter of determining who's right on that dimension (shaft diameter and spline count...) and the same dimensions of the hole in the FB NA clutches...:cool:

I really don't see the point of having a 6 speed in an FB. It will make the top end even lower than it already is as the Miata 6 speed has a higher top gear than ANY 5 speed mazda produced. 0.84 something compared to 0.81 as the highest on any 5 speed. You'd need a 3.7 gear in the rear end to compensate for the higher 6th gear ratio. Unless your engine is mostly stock or makes real crappy torque, its a pointless change IMO. A turbo engine would tear apart any mazda 6 speed anyway, and the gears would be too short for a turbo., making it only feasable on a NA engine.

Then you don't see the point in having fun or having a sense of adventure...;)

Thanks for the input!!:wave:

:cool:

You have it backwards. It means 5th gear will be more useable instead of having to shift to 4th all of the time.

The .825 sucks with 3.91 gears. The .711 or whatever the FC is 5th gear sucks even with 4.78 gears, not just because it is way tall, but it's also a huuuuge drop from 4th, so on the highway you're either at redline, or at only 4k.

I found the video, but the nVidia card on this computer is being a bitch. When I try to grab the video from the camcorder, I get the sound but a blank green screen instead of video. It's from my car with the 4.78 gears and the FC transmission... speedo is pointing something like 100-110mph, tach is barely showing 4000. One'a these days I'll put a 1st-gen transmisson back in this car, I mean it.

sorry to raise this from the dead... there are only a couple other threads about miata transmissions that i can find. I'm curious about swapping a 5 speed miata tranny' into my 83 gsl, the ones from the NA models, they are really cheap now. I'm getting a 12a aggresive sp built now, would these tranny's be able to hold up to our higher revving engines?

Also, a couple years after the fact... how have the swaps and altering the gearing worked out for everyone??

Thanks

so a couple of years later .... anyone get a 6 speed in yet :)

http://www.mazdatrix.com/faq/miatainputshaft.htm

people put the miata GUTS in to the rx7 case all the time. the miata trans is probably stronger than the FB, gearing is better too

cue the crickets....

i think my rx8 trans is actually going into an rx3. the shifter lines up with the rx3 (or SA).

in an FB the shifter will be in the radio, unfortunately.

For what it's worth, some of my Spec Miata buddies are of the thought that the 6-speed transmissions aren't worth the hassle. Apparently they don't hold up well in a road racing environment. (Disclaimer: I know they're not spec-legal)

lol ... that could swing both ways though. I have seen many threads that people figure things out and then just completely forget about this site or their thread update.

Bellhousing
 

What is the little gap by the starter I have a 79 Mazda rx7 and I didn't notice it tell putting it all together. and it seems to lead straight into the transmission I was wondering if this is how it's supposed to be or if there is something that is supposed to be there to close the gap.

Yeah, a little rubber piece. They're usually long gone.