KMiata has now developed a kit that allows you to use the ZF and Getrag 5 and 6-speeds from the E30, E36 and E46 behind either a Honda K-Series or a Mazda BP, as well as the BMW Getrag rear differential. It's a pretty interesting option and a big help to those who are making enough power to keep busting the Mazda transmission.
Interesting... I'd like to see a gear ratio comparison.
They have a ratio calculator on there site
The "definitive bmw trans ratios guide" http://www.bokchoys.com/differential/GearRatios.htm
That's awesome. (And that's a very good article).
Neat idea. The potential bug for me is it trades one of the best shifters ever made for one of the worst. Even after completely rebuilding it with all new parts, I was stunned at how crappy the shifter was in my E30. But with the solid ball-mount to the tunnel and a similar UC DSSR set-up, maybe it won't be too bad.
In reply to Ian F:
A DSSR and other upgrades do make those BMW shifters a lot better.
The gearing does seem a little strange. Seems like at the very most, you want a Miata 3.9 Torsen with the 6-speed. And the 5-speeds it looks like you want the 3.42 Getrag or numerically lower. Unless you enjoy 4000rpm+ cruising speeds.
So I could use this kit to put a K24 in my BMW right?
No, bad Hyatt, terrible idea....
Wonder what a Kswap costs?
It's amazing to see all of the cool stuff that is being made available for these 13-27 year old cars.
How common are limited-slip equipped BMW differentials??
Relatively common on e30/6 cars. E46 and up only the M cars got LSD>
K Miata isn't the only company working on this, they're just the only one that decided to go public 
NickD wrote: The gearing does seem a little strange. Seems like at the very most, you want a Miata 3.9 Torsen with the 6-speed. And the 5-speeds it looks like you want the 3.42 Getrag or numerically lower. Unless you enjoy 4000rpm+ cruising speeds.
BMW stayed away from OD for quite a while on their manuals. But that's not a bad thing. Lower gearing in the trans and a taller geared diff means lower driveshaft speeds. So the rotating weight of the driveshaft is less of a penalty (because you don't have to spin it up as fast) and it's easier to avoid driveline vibrations at high road speeds.
Its an interesting idea. Almost made me consider not going LS.
It'd be nice if it worked with Honda J-series too.
Also, how are BMW transmissions so tiny? I mean, seriously:
Very interesting. My NB is undergoing a turbo upgrade as we speak. Maybe it will eventually end up with a BMW transmission too.
dyintorace wrote: Very interesting. My NB is undergoing a turbo upgrade as we speak. Maybe it will eventually end up with a BMW transmission too.
I'm putting together a healthy BP-4W that may get turbocharged, and my 5-speed is kinda crunchy currently, so I'm also eyeing this with some interest.
rslifkin wrote:NickD wrote: The gearing does seem a little strange. Seems like at the very most, you want a Miata 3.9 Torsen with the 6-speed. And the 5-speeds it looks like you want the 3.42 Getrag or numerically lower. Unless you enjoy 4000rpm+ cruising speeds.BMW stayed away from OD for quite a while on their manuals. But that's not a bad thing. Lower gearing in the trans and a taller geared diff means lower driveshaft speeds. So the rotating weight of the driveshaft is less of a penalty (because you don't have to spin it up as fast) and it's easier to avoid driveline vibrations at high road speeds.
I'm limited to about a 60-65mph cruise speed because of driveshaft harmonics, so I'm getting a kick out of this comment...
Also, this is giving bad feeling in me regarding BP engines plus 325xi transmissions.
Bad feeling.
I don't even LIKE all wheel drive but when the fangle is there, you do what you must because you can.
Knurled wrote: Also, this is giving bad feeling in me regarding BP engines plus 325xi transmissions. Bad feeling. I don't even LIKE all wheel drive but when the fangle is there, you do what you must because you can.
Do these bad feelings involve turbo BP/K24 AWD buggies? 
Edit: You edited your post mid--post, so my post got kind of redundant. Weird. First time that's happened
buzzboy wrote: So I could use this kit to put a K24 in my BMW right?
That is an AWESOME idea. It's worth doing if only to watch the BMW fan boys' heads explode.
NickD wrote: It'd be nice if it worked with Honda J-series too. Also, how are BMW transmissions so tiny? I mean, seriously:
No... the BMW transmissions look to be a tad bigger in width. The Miata trans is only longer - likely due to integrating the shifter into the transmission housing. Add the BMW shifter and the overall assembly dimensions would be about the same.
Hey guys, thought I'd jump in to answer any questions.
Yes, we have a running, driving NB2 with a stock engine a 5 speed ZF trans, and it feels fantastic. We'll be pairing this setup to a 600whp K20 turbo setup very soon too.
Expect production parts to be on the shelf as soon as we're 110% satisfied with the durability.
To those asking about shifter feel, our setup does a few things to improve on the stock BMW setup and it's actually quite nice, and simple too. It's feels different than a 5 speed Miata trans, and much better than a Miata 6 speed. Overall it's a winning combo.
You can see the gear ratio calculator here: https://kmiata.com/pages/gearing-calculator
Quick, someone find a hooned E30 M3 and swap the S14 4 banger for a K24 hybrid.
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