I see builds with high hp and say the transmission lived. But rarely do you see anybody on the track with them flogging them for seriously low lap times, the true test of durability.

 

Im pretty sure I can pull the front bearing cover off my S15 box and put a miata front bearing cover on in its place. I will try that tonight.

 

I think repositioning one of the shafts within the housings is going to be essentially impossible. Using a V160 as an example of a similarly arranged trans, bearing seats would have to be moved in the tail and bellhousings as well as the thrust plate. It would be a huge undertaking to get things realigned. If the BRZ trans is stronger, but has the same spacing/length WRT to the shafts, then perhaps a bellhousing swap will be the easiest solution to get one into a Miata. I'll check that the bolt pattern on the midcase is close, or maybe even the same, and how the input shafts compare as well.

This is how I was thinking I'd make a rough estimate of the distance.

 

I don't know anyone around here who seriously tracks a BRZ, only open lapping days, and that certainly will be the true test of a high TQ build. There is a local BRZ making 470whp, I can talk to the owner and see if he's having any issues thus far, but he mainly drags it afaik.

 

Refresh my memory, does wheel hop kill rear ends or transmissions (or both?).

I would think that if he is dragging a BRZ that would bode well for this trans correct?

 

Rear ends and axles from wheel hop. At least that's what we mostly see. I guess there could be some damage upstream but there's a lot to break and upgrade in between first.

Edit: Dragging it will definitely find the weak spots on high tq cars, just not as quickly as road racing as there's typically less heat built up and sustained. And that car may be set up on boost by gear, if so it'll last longer on launch but not up top.

 

Confirmed, The front bearing cover from a Miata bolts on the S15 tranny shaft spacing is the same. I’d be willing to bet money the BRZ is also the same.

The input shaft on the S15 is way long. It uses a really tall throw out bearing and has a super thick heavy dual mass flywheel. If you try and use a miata belhousing on it it looks like the clutch disk may set too far back on the shaft behind where the splines end. I don’t think the BRZ version has this issue because it looks like the input shaft isn’t as long.

 

I'm going to take my 6spd to work tomorrow and grab some side-by-side pics with the BRZ trans, will post up asap.

 

pictures comparisons?!!!!

 

Sorry, I know that was quite a tease to dangle. I am actually working from home this morning and was planning on posting before I headed in.

In the short time I spent with them side by side, it looks like there are some differences that might rule out an entire cluster/shaft/fork/rail swap, but maybe some gears/synchros/hubs will move over to the NB 6spd. Will take pics of them once it's apart. FYI this customer says he's been at 400/360 for about a year on the trans.

Here are some resized shots. The link will take you to a Dropbox folder with the full size pics and a PDF of the BRZ trans service manual.

Edit: for reference, the shot across the face of the bellhousings was with the midcases aligned.


https://www.dropbox.com/sh/4zulo8pwe...rZfD5Uj9a?dl=0

 

I mean if you dont care about breaking the seals on the trannies you're so close to just seeing if the bell and tail housings swap.

 

Yeah, I left my 6spd at work and I feel like that'll probably happen lol. I can't guarantee it'll be this week. Gonna depend on my workload and when I can actually get to the BRZ as it's a low priority there. If I'm feeling frisky I'll go in off-hours and start it.

At the very least there will also need to be an input shaft swap or rework of the BRZ shaft as it is too long.

 

The S16 shaft is too long as well. So long I think if you did use a Miata belhousing on it you would have to add a spacer to the belhousing to keep the clutch disk on the spline section of the shaft if you did shorten the end of the shaft.

The casting on the center section of the S15 is Identical to the Miata however. Looks like there are some differences with the BRZ center casting and maybe some shift rods are in different places.

 

These are the first things I saw as well. Looks like those 3 sleeves in the bellhousing for the rods are a deal breaker on that end.

 

it kind of look like the miata has those 3 bumps they're just obscured by the fact that the clutch pivot boss is there, unless we're talking about a different feature.

 

I've added to the dropbox folder a closeup of that area on the NB trans where the difference is more obvious. I was hoping that the end plate on the NB housing was thick enough to hide the ends of the sleeves and accomodate the pivot ball bung, but I'm not holding my breath.

 

I think it is, you can see one of the bumps right above the pivot ball, and it looks like the flat section below the pivot ball is higher up than the flat section above it, probably at the same height as the bump, or that last part could be a trick of the camera.

 

Very fast FR-S at Super lap last Friday. Definitely not a stock gearbox. I wonder what it was.

 

The flat area from which the rail sleeve and boss protrude is the same height everywhere around those two features. However, the rail sleeve protrudes less on the NB than the BRZ, leaving open the possibility that the other two rail sleeves could be hidden in the NB casting.

I don't have the NB manual in front of me and don't know the trans internally, so I can't say for sure.

 

Question is are all the shift rings in the same place on the shafts. Wonder if all the shafts and rotating bits could move over and have the Miata forks and shift rods shift it in a Miata housing.