500Nm of Torque in the NB 6-speed Transmission
 

Did you know that the Aisin AZ6 6-speed transmission from the nb2 is also used by Toyota and Nissan in cars like the Lexus IS200 or the S15?
Did you also know that by modifying the countershaft you can reach a torque of 500Nm? Here are two articles for you to take a look ...

https://www.sq-engineering.com/tech-...ication-guide/

https://neatgearboxes.wordpress.com/...x-circlip-mod/

What do you think? Did you know about this solution or had you researched this topic?
It seems something interesting ... or maybe I'm wrong
elpazos aka IG @jrmiata

Post update: a few months ago I made this mod on my car and I am very satisfied with the results, after 2 trackdays and intensive road use there have been no problems and the transmission works perfectly. The car makes 400hp and 500Nm of torque and I have installed a ceramic double disc clutch, therefore the transmission must withstand greater loads. So you can imagine the level of power this mod can achieve. It is the first Miata to make this mod, it has never been done before and it really works.
The countershaft modification was done in Neat Gearboxes. Who wants to request the measurements to DIY send me a DM. See my post where I explain the assembly procedure:
Aisin AZ6 6-Speed Gearbox “CIRCLIP MOD”

You're onto something. Props. Think we'd give this a try in the next few months to come.
edit: Also reading the miata variant is called Y16M-D, while the articles relate to J160, no mention if the same mod applies to a Miata AZ6.

The basic Aisin AZ6 gearbox was made in several versions, with front cases for these engines:

• Nissan FS6R30A (source: Nissan pickup 2004-)
• Nissan FS6R31A for SR20DET (source: S15)
• Nissan FS6R31A for VQ35 (source: Z33)
• Nissan FS6R92A for VQ35 (source: G35) 130 lbs weight
• Nissan FS6R92A for SR20 (source: S15)
• Mazda Renesys (RX8 rotary)
• Mazda Y16M-D F & B (1999-2005 MX-5)
• Toyota J160 for 1G & 3S (E10 Toyota Altezza/Lexus IS200)
• Toyota 86/Scion FR-S
• Subaru BRZ

The source:
Tech Wiki - 6-speed : Datsun 1200 Club

https://cimg9.ibsrv.net/gimg/www.mia...d099dd1787.jpg

• December 1997– AZ6 — 6-speed
  • Mazda MX-5/Roadster/Miata, Nissan Silvia, Mazda RX-8, Toyota Altezza/Lexus IS200, Toyota 86/Scion FR-S/Subaru BR-Z

Source:
https://en.wikipedia.org/wiki/List_o..._transmissions

Well, I think I'm not wrong and the transmissions are the same. So it could be great news! Simply by taking the countershaft to a machine shop and making the modification described in the post we could have a very significant improvement in our transmissions with a gain of 500Nm!
At first glance it does not seem complicated and it would be easy to test. In my case I have already destroyed 2 transmissions and this opens up a world of possibilities ...
elpazos aka IG @jrmiata

Confirmed! They are the same gearboxes. I have sent an email to the guys at Neat Gearboxes and they have confirmed that the modification can be made in the 6-speed transmissions because the counter shaft is exactly the same as in the Nissan Silvia S15, Z33, Lexus, Toyota etc. I reproduce the answer below:

Hi Ramos,
Yes, the clip modification works for the Miata / MX5 6-speed transmission, we have done at least 5 or 6 Miatas.
While I don’t have any lab testing or anything, we do have over 60 of these in the real world being used since 2015. I have seen one break in a BRZ with 303kw@wheels. And in fact, it was not the clip that broke but 4th gear itself. Other than that, I don’t think I’ve heard of any breaking with our modification.
I have a Lexus IS200 with a turbo charged BEAMS motor. it is on run-in tune but will be easily capable of 300wkw. I have done the C-clip modification to that gearbox too, so it will be a good test.
The difficulty is that the shafts must be sent to us in order to machine them correctly to suit our larger, stronger C-clips. It does make logistics a little harder and more expensive.

Kind regards,
Sam Charlick
Owner/manager
Neat Gearboxes

It is a really economical option compared to other solutions such as Kmiata and its conversion kit to BMW transmission.
elpazos aka IG @jrmiata

Interesting. I wonder if something one the shops state side could pull off.

If the rx8 and brz boxes are the same does that mean they're adaptable? Rx8 transmissions are far cheaper than miata 6 speeds nowadays...

Not likely. The input and output shafts are likely to be different lengths. Just looking at pictures of some of them, the tail shaft on the NB variant looks much longer to retain the internal shifter.

This is great news! I've been following this thread since it popped up. Lucky me for once being in Australia :D Will be far cheaper than a BMW trans swap for me.

Some time ago I came across the same source and managed to contact Neatgearboxes and asked if the reinforced gearbox would withstand my assumptions (around 500hp and flat 450nm of torque). Unfortunately, they are not convinced about it, let me paste in the answer.

For me, the game is not worth the candle, I was fixated on the point of staying with the stock gearbox, but to strengthen it properly for such powers, in my opinion, you would need to make a C-Clip mod from Neatgearboxes and strengthen the rest of the gearbox, e.g. in Walter Motorsports (but the 6-speed gearbox is work in progress). My case is slightly different because I would have to import everything to Poland, which drastically increases the costs of the project.
I could decide to do it, if I was sure that the gearbox would be bulletproof, but I do not have such certainty, and if something happens to it, even not necessarily because of its durability, I'm left with huge costs to bear, in addition, I have to wait six months until another gearbox can be strengthened in two companies at two corners of the world.

For these reasons I decided to swap to ZF 8hp70, at least in my country this gearbox is cheaper than the 6speed from Miata, it shift very very fast and it can handle around 1200nm of torque. The swap cost is comparable to or even lower than building a 6speed Mazda. When I sell my clutch from SuperMiata (around $ 1,400), I have already covered about 70% of the costs.

Hey Henorek! I send you a DM

I can do this in my shop if people are interested.

I stumbled across this thread just punching in circlip mod in Google

I have a Nissan S15 that has just completed this modification (and extra bits), I did things a little differently but happy to share prices, approach and the outcomes as I break the box and diff in over the coming weeks.

What is the upgraded clip made from? Better options? Does it need heat treated and/or cryo treated? Do you assemble the whole gearbox? Thanks.

I can make it out of what ever you want. I use D2 tool steel for my own, heat treated.

Curious to know where these can be found, as in what is/are the source vehicles.

Thanks in advance.

This gearbox runs in a truly countless number of cars. So it will be most convenient to link to Wikipedia. The difference between the manufacturers is mainly the bell of the transmission which forces a different adapter.
https://en.wikipedia.org/wiki/ZF_8HP_transmission

Thanks. Not sure I am ready to step up to an auto.

Nevertheless, I'd be interested in your build thread for this conversion, particularly for the adapter and controls electronics. Please keep us informed.

This is an awesome find. Good job OP! Far more palatable than the Kmiata BMW trans swap.

Anyone here running this?

I am seriously considering giving this a shot with my spare 6 once I get the EFR on. Would be huge if it's this simple since it should support *most* people's built power goals.

I have heard firsthand that 2 smaller entities are developing more cost-friendly bmw trans swap solutions, so I'm also on the fence until those are released

That’s exactly what I’m thinking! It’s a big deal if we can max out an EFR on pump gas and have a reliable 6 speed for a relatively small outlay.

Post update: a few months ago I made this mod on my car and I am very satisfied with the results, after 2 trackdays and intensive road use there have been no problems and the transmission works perfectly. The car makes 400hp and 500Nm of torque and I have installed a ceramic double disc clutch, therefore the transmission must withstand greater loads. So you can imagine the level of power this mod can achieve. It is the first Miata to make this mod, it has never been done before and it really works.
The countershaft modification was done in Neat Gearboxes, see my post where I explain the assembly procedure:
Aisin AZ6 6-Speed Gearbox “CIRCLIP MOD”

Good to know. Have you done it yet, or has anyone taken you up on your offer?

Who wants to request the Circlip measurements send me a DM

Very interesting. I've got a spare 6 speed laying around, I might have to go this route...

ncjake I’d definitely like to get this done. How else can I get in contact with you to work out the details?

Sorry for the bump and probably a noob question, but does this mean that these transmissions can be swapped into NA instead of NB 6 Speed ? By changing front case, or even without changing and just getting an adapter plate?
As you can guess, 6 speed is very hard to get here, impossible to legally import 2nd hand car parts but other transmissions on the list can be found, even order a brand new BRZ trans (probably for the cost of a kmiata e46 swap kit)

You will have the same problem since you should also disassemble the transmission and make the modification of the circlip to reinforce the countershaft. As far as I know, the transmission of the RX8 changes the bellhousing and the main shaft is not compatible, so you would have to change these 2 components, I do not know the adaptations that should be made in the Silvia or in the IS200

it is ok, I will already be happy to move away from the glass cannon 5 speed, I am targeting more or less what I can get from a TD04 so, 300 bhp at best. Rear is already 1.8 torsen, only weak link is tranny. I guess there would have been swap kits etc. produced already if it was an easy swap, but I wonder how difficult it would be. Labor and machining costs are acceptable here, just do not want to get into fabrication too much.

no, the BRZ transmission does not swap into the NA/NB.

It really would not be worth doing.

Where and what is the name of the shop?

Hows that 4th gear holding up? That is many powers.

Awesome to hear it!


And for final clarification, the only thing done to the trans was the circlip mod?

Also, a tidbit of info in reference to the RX8 compatibility, *the bell housings can be swapped between the two but the tail shaft is much longer. The shifter would be about where the trunk release is in an NB. Looking at Alldata, I figured the gears could be swapped around but not sure if the output assemblies/tail casings are interchangeable. I picked up a $200 RX8 trans last year and these were my findings before deciding I was in over my head and returning it.

Has anyone in the states had this mod done? I'm looking for a shop to do this to my 6 speed while it is apart.

Any machining workshop can help you, all you need are the measurements. Send me a DM to know more...

I contacted Jacks Transmissions and they said they could do the 4th gear modification. They're familiar with the AZ6, because they build the FRS/BRZ trans. I also asked them if any of the BRZ modifications (carbon fiber synchros, gear sets, shift forks, bronze shift rail bushings, etc.) can be applied to the Miata AZ6 and there is basically nothing interchangeable between the two. The term AZ6 just defines the basic architecture of the gearbox.
They could rebuild the box with OEM parts, perform the 4th gear mod, and micropolish or WPC treat the internals. So I got disappointed and have given up on the stock trans given that my complaints with it are: it shifts like stirring a bucket of bolts (even with MR shifter), locking out 5th gear on track, and reliably holding 300ft-lbs.

Question.... Do we know the reason for locking out 5th gear on track? have this problem... an for now havent tested yet is to put a oil cooler so that the gearbox doesnt get to hot.... thats the one solution i could think.

The reason is that the 3rd and 5th gears are too close together, so sometimes you can engage the 3rd gear. If you move the lever beyond 5th you go to the reverse gear rail and it doesn't engage. Look at my last trackday and 33 seconds from the end you can see how this happens:

most probably then my problem is the engagement of reverse gear rail is there any trick we can do to block somehow the reverce at least in track... maybe a stoper at the gear leaver?

Correct there are gear levers with this function, this will be my next improvement:
https://cae-racing.de/CAE-Ultra-Shifter_1651

Ive had a journal bearing remove itself from the shift fork and have seen a seized pivot bolt (the donotremovethisbolt bolt) prevent or hinder 5/R usage.
when i had my box open, i stretched the reverse lockout spring some and it mightve helped? Ive yet to miss 5th or pop towards R since but im streetcar and the MR shifter fixed most of my gripes.

Just an update... Cae Shifter worked great Job done... shifts are precise and no problem with 5th gear & reverse. Next change make the transmition hold 500Nm...

https://www.dropbox.com/s/r3861qk0n7...13690.jpg?dl=0

Would that be Jacks transmissions in Colorado Springs, CO?

Hi guys, i watched this thread for ages as i was building up my car. last week it had the final tune and made 411whp with 480nm of torque. retained the 6 speed but had Neat work their magic. the car will do a couple track days here and there but its mostly just for the daily commute and some spirited driving up the local mountains. ill let you guys know if anything happens with the boxhttps://cimg9.ibsrv.net/gimg/www.mia...9f1f8b91ff.jpg
https://cimg0.ibsrv.net/gimg/www.mia...db28d63511.jpg

That looks like a killer setup

Oh, a Brisbane man! I hadn't heard of Capalaba Motor Repairs, but it looks like they do good work!

Any more details on the build? Are you running E85 or 98?

I wondered who was going to notice that ...

Nice car, good HP!!, I hope you have bonnet vents, that's a lot of hot pipe up there. Also be interested in your experience with the Neat mods, please post more about how everything goes in use.

Been going to Rick and Terry at CMR for a few years now and they do top notch work. This time round I came to them with a list of parts I had in mind and a few requirements, they made a few suggestions and they executed the build exactly how I wanted. They have a dyno in house so they were able to do everything to the car minus the engine machining, powder/ceramic coating and obviously the gearbox work. Heres a screenshot of my spread sheet with all the parts done to it, and yeah the car runs straight E85
https://cimg6.ibsrv.net/gimg/www.mia...1206dbc860.png

I will definitely bump the thread if I end up munching the box but I am a fairly sedate driver relatively speaking and ill probably avoid clutch dumps and hard launches.
I do have a set of Wilvern motorsport vents but haven't yet installed them. The car has been perfect temps so far on the street and the intake is tucked in the arch with a temp sensor and all is well there also. not sure how well the catch can lines will hold up though so I'm keeping an eye on that. Any other reason why vents would be a must that I'm unaware of?

Properly sited vents exhaust hot air from the under-bonnet, reducing temperatures but importantly aiding flow through the radiator by reducing under-bonnet pressure. Have you done the ducting exercise - blocking avenues for incoming air to bypass the radiator? Without this much of the incoming just passes through engine bay bypassing the radiator, not helping cooling any. I don't know if they are a 'must', but at that power level in Brisbane I'd suggest they are advisable. The proof of the pudding will be coolant temps, I'd be looking at your logs on those, and maybe setting a big warning on the dash using the PS readings. PS1000, not clear in the above?

Yeah, I'd be avoiding those hard launches too, that would be asking for trouble! But you have paid for that grunt, I'm guessing you will be using it, putting that through that box will be testing it, however it is done. I have a spare box I am keeping for just-in-case, I am not at that level and don't plan on getting that far either, but I haven't done the mod either.

I have a shroud and also a cooling panel to help direct airflow through rather than around the rad and yeah I have already programmed some warnings into the ic7 dash for coolant temp. Again signs of potential overheating on the the street, done about 700km through both traffic and highway so far.

I figure if this box pops I'll go with the typical BMW conversion but I wanted to keep everything as "Mazda" as possible.

You need a whole lot more to do a proper job, search here, or just look closely at the front, the gaps are everywhere. However, if your temperatures are ok (in range) then you probably don't need to go to those lengths - just be aware that there is scope to further improve your cooling.as/when the need arises.

Note, shroud limits flow when moving, useful in traffic though - but, again, if it isn't broken don't fix it.

Yes, the BMW seems to be the go-to for replacing the AZ6, but eyewatering cost, especially as $A dropping against $US.

100% increase in power in 600rpm! (3700-4300) That would be an interesting daily commute!

awesome build btw..