mazda rotary transmission knowledge/help my engine swap with knowledge/parts bin engineering

I currently have an NA miata, I also currently have a lexus 1uz 4L DOHC v8. They will be put together, I'm just having second thoughts on transmission choices.

Recently I noticed you can adapt the 1UZFE to a Mazda FC3S RX7 transmission. (fine print in ebay ad HERE )

I don't quite understand rotary nomenclature; but I am under the impression that the 13b would have the same bellhousing pattern (with different starter and slave cylinder locations). As the starter in in the v of the lexus engine and the flywheel is custom, that shouldn't matter.

From what I understand with roatary transmissions, there are a few options. There is a NA box with little changes throughout the years (called a SA for early trans FB for later trans?), there is a turbo box on the T2 (called a model R?), there are ND boxes (which look a lot like the T2 box) and there are rx8 boxes, which I have no idea what they share in common.

From what I understand the non turbo rx7 transmissions can be mix and matched with the miata transmissions. It appears that the "bellhousing" and "tailshaft" can be swapped from the transmissions with modification or swapping required on the input shaft. This is mostly done by Rx7 guys to get the miata ratios and newer boxes in their cars.

nonturbo bellhousing and miata bellhousing

To add to that knowledge, the turbo box differs from the NA boxes with a different bellhousing (is wider to hold a larger clutch/flywheel, and separates from the transmission at a different point). The transmission is beefier. But what I believe is true is the "tailshaft/shifter turrent" is still a similar design and can be swapped. This is where I'm assuming things.

Pictures for knowledge: Miata box

Rotary NA boxes

Turbo rotary box

What I want to do, is put the miata's tailshaft/shifter on the turbo 2 transmission. I'm not sure it can be done, but turbo boxes are not easy and cheap to find and I don't want to buy one that wouldn't be what I'm thinking.

non turbo box tailhousing swap, incomplete (the mentioned ballancer is wedge fit on and held with that giant nut) miata rotaries

Non turbo trans(same bolt pattern as miata, with ballancer)

turbo trans

turbo box with tailshaft removed FD box(looks different....)

Comparing 89 FSM's, they look non compatable

TL:DR I want to put a miata transmission tailhousing on a rx7 turbo transmission. I don't know if it will fit. I know I should be able to swap with a 1uz->adaptor->rotary bellhousing->miata transmission PPF and stock diff. What I want is 1uz->adaptor->rotary turboII transmission-> miata trans tailhousing PPF and miata diff.

Thanks for looking!

Nothing at all interchanges between the ribcase (Turbo) and smoothcase ('79-92 nonturbo, Miata NA/NB) transmissions. So what you want to do is not possible. Everything is completely different.

The FD transmission MAY allow you to do what you want, as it had a PPF and is the same design as Turbo II. Don't know if they screwed around with input shaft length, they may have as they went from push clutch to pull clutch at the same time.

The RX-8 might be your best bet. It and the NC maita share the same basic subframes, PPF and transmission (close enough anyways).

Big difference transmission wise is obviously the bellhousing.

Ask questions. The adaptor probably requires a certain starter to work. RX-8 and Turbo II have a large diameter ring gear, N/A have a small diameter ring gear, and the starter attaches to the transmission so the flywheel OD is important.

If it's for an N/A... just walk away. That would be the easy button (Miata tailhousing on N/A transmission) but transmission life will be ludicrously short. RX-7 transmissions are weaker than Miata.

Interestingly, there is a swap setup in the works for putting a 350Z transmission in an RX-7. Supposedly they shift just fine at 9000rpm+ yet have enough strength for turbo engines.

I have 3 transmissions in my shop- an NA Miata, an FC turbo, and an RX8. I can tell you there is nothing similar about the Miata trans and the others.

The Miata and the RX8 both use PPLs (though they are different). The FC uses a conventional trans mount.

RX8 guys have confidently told me you can't swap the tailpiece from an FC- I've measured them, and I'm pretty sure they are full of crap- the taIlpiece flanges appear to be identical (though I have not swapped them yet).

The RX8 assemlby is 1/2" longer than the FC.

I am mounting the FC trans in an RX8, and decided I need the PPL to do the job right, which means I need the RX8 tailpiece.

Your challenge with the Miata is that it needs a PPL, but the RX8 PPL is not very useful for you, and the Miata tailpiece won't work. It might work better to use the FC tailpiece, and build a trans crossmember so you can use an FC trans mount.

Assuming the mating flange between the trans and the engine is in the same location as in the NA, the shifter position of the FC trans will be too far back. This might be a bigger problem- if you use the FC and the 1UZ, you will have to push the 1UZ forward to get the shifter position right, which is the opposite of what you want for weight distribution.

I'm interested to hear more about your efforts, because the Miata wth a 1UZ is definitely something hat interests me.

For alternative sources for the rib case transmission have a look at Mazda b2600i trucks and manual rwd mpv vans. Be aware, gear ratios vary across the rib case boxes. Im pretty sure solomiata has a ratio guide on their site.

You'll still need a rotary bell housing to use with the 1uz adapter.

Forget about using the smooth case transmission, you'll just end up shattering it.

As a side note, if anyone comes across a mpv v6 manual Transmission, sell me the bellhousing, because v6 b series swap.

SVreX wrote: I have 3 transmissions in my shop- an NA Miata, an FC turbo, and an RX8. I can tell you there is nothing similar about the Miata trans and the others. The Miata and the RX8 both use PPLs (though they are different). The FC uses a conventional trans mount. RX8 guys have confidently told me you can't swap the tailpiece from an FC- I've measured them, and I'm pretty sure they are full of crap- the taIlpiece flanges appear to be identical (though I have not swapped them yet). The RX8 assemlby is 1/2" longer than the FC. I am mounting the FC trans in an RX8, and decided I need the PPL to do the job right, which means I need the RX8 tailpiece. Your challenge with the Miata is that it needs a PPL, but the RX8 PPL is not very useful for you, and the Miata tailpiece won't work. It might work better to use the FC tailpiece, and build a trans crossmember so you can use an FC trans mount. Assuming the mating flange between the trans and the engine is in the same location as in the NA, the shifter position of the FC trans will be too far back. This might be a bigger problem- if you use the FC and the 1UZ, you will have to push the 1UZ forward to get the shifter position right, which is the opposite of what you want for weight distribution. I'm interested to hear more about your efforts, because the Miata wth a 1UZ is definitely something hat interests me.

If the rx8 and rx7 rib case have some interchangeability that is awesome. I can get rx8 transmissions way cheeper than the rx7 and a 6 speed b series would make me a happy person. Can you confirm if the bellhousing swaps between the two?

There's a company out there that has built a few 1uz miatas, my partners uncle has one, its pretty badass.

Edit, Bullet cars

I can confirm it next weekend.

No worries mate, it would be very much appreciated. Google image searching has been less than conclusive.

Thanks for the heads up everyone. After looking at the FSM pictures its pretty obvious the turbo trans and the N/A trans do not have interchangeable tailshafts. For some reason I remember reading in some mazda literature that the tailshafts were of similar pattern, but I obviously am remembering incorrectly.

SVreX wrote: I have 3 transmissions in my shop- an NA Miata, an FC turbo, and an RX8. I can tell you there is nothing similar about the Miata trans and the others. The Miata and the RX8 both use PPLs (though they are different). The FC uses a conventional trans mount. RX8 guys have confidently told me you can't swap the tailpiece from an FC- I've measured them, and I'm pretty sure they are full of crap- the taIlpiece flanges appear to be identical (though I have not swapped them yet). The RX8 assemlby is 1/2" longer than the FC. I am mounting the FC trans in an RX8, and decided I need the PPL to do the job right, which means I need the RX8 tailpiece. Your challenge with the Miata is that it needs a PPL, but the RX8 PPL is not very useful for you, and the Miata tailpiece won't work. It might work better to use the FC tailpiece, and build a trans crossmember so you can use an FC trans mount. Assuming the mating flange between the trans and the engine is in the same location as in the NA, the shifter position of the FC trans will be too far back. This might be a bigger problem- if you use the FC and the 1UZ, you will have to push the 1UZ forward to get the shifter position right, which is the opposite of what you want for weight distribution. I'm interested to hear more about your efforts, because the Miata wth a 1UZ is definitely something hat interests me.

This is also great information, as the rx8 transmissions look very close to the TII trans, but are much easier/less expensive to get a hold of, and it rules out the rx8 transmissions from my plans.

I currently have an ax-15 which shares a r154 bolt pattern, so I could adapt that and build a transmission mount (as originally planned) I was just daydreaming about an easy inexpensive non-truck like shift.

Now I'm currently flirting with the idea of using the 13b bellhousing bolted to the miata transmission unmodified. Just like: This miata with a different engine. Turbo guys seem to blow up their boxes with WHP and wheel torque just above what the 1uz makes at the crank, I have a 1.8 diff to swap in anyways.... Stay tuned, for a couple of years...

Knurled wrote: Ask questions. The adaptor probably requires a certain starter to work. RX-8 and Turbo II have a large diameter ring gear, N/A have a small diameter ring gear, and the starter attaches to the transmission so the flywheel OD is important. If it's for an N/A... just walk away. That would be the easy button (Miata tailhousing on N/A transmission) but transmission life will be ludicrously short. RX-7 transmissions are weaker than Miata. Interestingly, there is a swap setup in the works for putting a 350Z transmission in an RX-7. Supposedly they shift just fine at 9000rpm+ yet have enough strength for turbo engines.

The 1uz has a v-mounted starter (engine intake valley), and will use a modified flywheel with reversed ring gear, so its a mash up of parts of clutch disk spline and diameter with differing flywheel/pp stuff without worrying about starter placement/flywheel diameter on the trans. If I decide on trying to keep the ppf, I will use a later miata box with the rotary bellhousing.

In reply to daytonaer:

Check to make sure that it all works. One of my friends in the know was taking about the 6 speeds and said while they look the same, nothing interchanges, RX-8 have larger input and output shafts and the bearings are correspondingly larger. But I don't recall what 6 speed he was talking about, there are two different ones.