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.