Is there a way to do an LFX swap and keep the miata diff?
 

I know the PPF goes away with the LFX swap. I currently have an OS Giken LSD and would like to keep the miata diff and axles to save a bunch of time and money. From everything I have read they should be able to handle the LFX power so it doesn't make it necessary to swap over to the GM diff and custom axles.

Is there currently a way to remove the PPF and keep the miata rear diff?

I believe KMiata is working on a PPF delete, though it's not on the market yet.

I would also like to combine a non Miata transmission with the 1.8 rear and when I mentioned it in the kMiata BMW transmission thread, they said they were working on that as an option.

Yup, we have a bolt-in PPF delete getting close to hit the market. We've already made a couple sets and just want to do some more brutal testing before they are up for sale. They will be suitable for street cars and race cars, with a range of durometer ratings for the front poly bushing. I'll definitely post about them here when they are ready to go.

LukeG, not sure how that LFX trans is geared, but you may need a longer rear end to make it all be happy together. I think V8R is normally using a 3.42 Getrag for those cars? Not sure, but worth checking out.

Awesome, thanks! I think you'll sell quite a few of these.

Yeah, I looked at the gearing and a 3.91 even with the MV7 with lower trans ratios would be ridiculous. Needs to be a 3.42 or 3.23 in the diff :P

I saw one person's way of doing this in a thread here, a week or so ago. It involved a custom bracket securing the diff end of the PPF to (IIRC) the side of the tunnel. The rest of the PPF is cut off.

Best I can do I'm afraid.

Just make a flat bracket for the front, cut the front mounts off, and turn the ppf into a torque arm.

https://www.miataturbo.net/build-thr...3/#post1474294

It got tested this past weekend in an enduro and appears to have passed with flying colors. Not recommended for street cars since this design is straight metal on metal with zero vibration isolation. The KMiata diff mount will be a better solution for most people. My diff mount might be for sale eventually, but not until my own car is up and running and I've put significantly more test miles on this design.

Came across this old thread and pic searching. Interesting idea.

https://www.miataturbo.net/suspensio...-delete-69312/

https://cimg1.ibsrv.net/gimg/www.mia...fe06ecafee.jpg

^^ Isn't that essentially just a very short torque arm? I can't imagine that it'd be very effective, unless the diff had solid bushings.

Yes. With IRS it doesnt matter because the rearend doesnt move. The only leverage against the chassis is the rear sway vs lca angle changing.

IIRC that one broke. Thats why you see on mine I put a huge amount of steel on the rear sub frame so that I would have a ton of weld area to the subframe and not tear out. Also you need more than that, because theres play in the rod ends, You should also put a cross brace under it with a bolt to preload the rod ends up which is the directions they go under acceleration.

PPF delete issues aside, keeping the Miata diff with anything but 3.6 R&P would be absurdly low geared, really need lower like a 3.42 or a 3.23. Plus at LFX power levels the Miata diff is going to have borderline reliability anyway.

Do those ratios even exist for the Miata rear at anything resembling decent prices or availability? I looked in to getting 3.6 gears a while back but it was an expensive pain in the ass. This was years ago however.

There have been multiple attempts at doing a 3.3 rear gear set group buy over the years, but none of them have gotten then number of people needed to make it happen.

There was also a rumor that an 80's mazda truck 3.3 rear set would work, but from what I have seen that has been disproved. So as far as I know nothing under a 3.6 ratio exists.