Folks have sheared 2,3,4,5 gears on AZ6's at 300-350 lbs. When shifted fast on track where trans temps are high and the aluminum shift forks start to bind in the steel grooves they sit in, folks get them either stuck in gear or unable to engage. Shifting improves once they cool down but the damage is done by then. Of all the cars produced with AZ6's, only the 99-05 Miate had aluminum shift forks. And no, the steel ones don't fit. Yes a few folks have investigated beefier shift forks and they are not cheap.

Still no relatively cheap PNP alternative with ideal ratios exists. BMW ZF conversion from Kmiata is robust but not cheap and ratios leave something to be desired unless you spring for the pricey 6 spd option (~$5000). Quaife is noisy, ragged on the street, has perfect ratios and costs about $11k to complete.

The reality is that a PNP 400lb tq AZ6 solution with syncros and good ratios is going to cost ~$4k and even that is more than most of the Miataverse is willing to spend. So the ROI to develop all the proprietary internal bits of a AZ6 "Superbox" just isn't there. The half dozen or so guys that would click buy tomorrow, won't be enough. We'd have to sell at least 50/yr with no warranty returns to make it worthwhile and even then its a low margin product for us. We spent about a year working with a few suppliersr and decided the margin just wasn't there for us. Walter Motorsports is currently the best bet for a beefy AZ6.

I miss my big-power '93 but I don't miss all the shenanigans caused by the lack of a strong-enough transmission. I went through two Quaife gearsets (installed in a 5-speed case), both of which died on the track. After investigating and eventually discounting the KMiata conversion option, I installed an MSM 6-speed about a year before I sold the car in preparation for getting my 30AE. After all those years of chasing horsepower, I'm now perfectly happy with less than 200 normally-aspirated horsies. I'm really enjoying a car that you have to cane in order to pass on a twisty back road, rather than roll on a half-inch of throttle to surge by on a tsunami of mid-range torque. If I have to slum it, power-wise, it's not a bad way to go.

If I had 500 or more hp, I personally would seriously consider either a G-Force GSR or GF-5R transmission.

Thanks for the info man great reply. Question, I checked Walters site I only saw the built 5 speed. I guess they also can do an az6?

They list it as under development.

https://walter-motorsports.com/shop/...ission-6-speed

I just noticed that. I was on my phone. On my laptop I see that it's in development. I just emailed them to see what they say about it. I'll send them my broken 6 speed that's sitting in the basement tomorrow. Lol

We sort of initiated tha AZ6 project with him but it stalled for costs. There just isn't room for margin for supermiata to be included. So he's continuing to develop the AZ6 amongst the many other projects that he has going. He has delivered several upgraded AZ6s to customers. But it is an evolution, it is not as if it is a single specification.

Sort of derailing this thread with talk about transmissions but one critical factor that is sort of a deal-breaker for a lot of users, is that any blueprinted transmission must be broken in. If it is not broken properly it simply will not perform the way it's engineered to. We have one of the early prototype AZ6 boxes in one of our cars. Busy with other projects, we have not run high boost through it. I will say this though, it shifts better than any Miata transmission I have ever used.

Yes, sorry to go off topic on the thread. Appreciate your info on the trans stuff. I emailed them and I think that's the route I'm headed.

Update to the original post. After using some of my suggestions on cam tuning, the owner was able to improve the spool mightily. 500 lbs torque at 4000? Yes please.
This particular longblock is safe to about 8500 but you can see the short duration cams doing their work with a 6000rpm power peak and 4200 rpm torque peak.
I don't recall the specs but, turbo BP's used for auto-x or track like short cams and lots of lift.
https://cimg8.ibsrv.net/gimg/www.mia...a701e70237.jpg

That is a monster, nice work.

That is beautiful