I think the implication is that you may not be able to use the RX-8 bell on the Miata gearset because of bearing/shaft dimension differences.

 

I have no proof yet but I suspect that not to be the case.

Not that the RX-8 ratios are that much worse, 4th gear just annoys me

 

ive had both apart, and the cases do look the same, but the internals on the Rx8 are way beefier.

 

So, if the parts technically bolt together, that means they will work right?

 

Hm, so the internals aren't identical after all. Annoying.

Having neither of them here, would it still be practical to move the bellhousings over? Yes, if the Miata internals are weaker the torque capacity will be less, but turbo Miata guys seem to make more torque through Miata 6 speeds than any NA 13B will. Or should I just stop the pipe dream and save for a dog gear set in the 5 speed?

 

yes.

thats the thing, it LOOKED like the bellhousings would swap, but i'm not sure if they actually do.

it should be really easy to find someone selling an early Rx8 6 speed, because they swapped in the 09 6 speed for no real reason

 

Dog engagement is sick. but I do not know for street use how fast it will wear out. also if you are not focussed and mis shift at 10K from lets say 2nd to 1st instead of 3rd then bad things can happen as this kind of gearbox does not hesitate and you do not use the clutch to shift up.

Here is some info from my built.
https://www.rx7club.com/naturally-as...eakup-1000801/

Here a movie from dog engagement with straight cut gears

here is for comaprison our miata with stock renesis and rx8 6 speed.

On the same racetrack with the dogbox and decent ratios we use 5 gears and with the rx8 6-speed one only has to use 3rd and 4th gear.. Also I suspect the rx8 6-speed (or any helical cut) to be way less efficient than a straight cut box. as for instance with the rx8 6-speed we had to run a 15 row oil cooler and pump to keep the oil temp in the box under control (<130°C) where as with the straight cut dogbox we run at least 50hp more and oil gets barely over 80°C

if you solely go for street useage and not want to race I think the RX-8 or the miata 6-speed might be a valid option but for track use I would stay far away from it.

 

I was thinking dog engagement only on 2nd and 3rd gear, because even with 4.78 final drive, third gear is good for over 100mph, and I've never had a problem downshifting into 1st when I wanted to but always had a problem upshifting to 2nd and 3rd gear.

 

my Tr3 had a non synchro 1st, and if anything they should have had a synchro 1st, and a non synchro 4th/top...