mr2daj

iTrader: (-1)

info for the ratios i was recommended by the builder:

mr2daj

iTrader: (-1)

ratios that sav recommended:

emilio700

iTrader: (3)

Keep in mind the static loaded radius is what determines tire drive ratio, not circumference of a new (full tread) tire when measured off the car. I measure a typical 225/45/15 used race tire hub center to ground distance at closer to 11.2" when inflated to race hot pressures. This affects speed in gear calc quite a bit.

Savington

iTrader: (31)

+1. IOW, GPS always says you're going slower than your gear calculator says, typically by around 5%. My ratio recommendations are based on knowing what I want when compared to 6-speed ratios (longer 3rd, same 5th, 4th in the middle, shorter 6th), not on a desire to hit certain MPH targets in gear. If you need more MPH in a gear for a specific track, that's when you raise the limiter or change the rear end.

The ratios your builder suggested are close enough to ideal that I wouldn't worry about it.

Savington

iTrader: (31)

Input/output shafts will be different. Wouldn't be impossible to overcome, but it'll still require custom parts.

Impuls

iTrader: (1)

Still less than +$3000 though?

sixshooter

iTrader: (12)

Wouldn't the toughest hurdle be the bellhousing and PPF mounting points? I would like to hope the input shaft could be interchanged with the one out of a Miata, but I've not ever had a 6 speed apart so my musings are speculatory.

Savington

iTrader: (31)

Easier than you might think, I suspect. I bet all the bearings, etc. are the same, and I know the center sections are identical, so I think a Miata tailshaft and bellhousing would bolt up to an S15 6-speed.

NiklasFalk

iTrader: (1)

Didn't bbundy say that the rear shaft was shorter and different than the miata one. The input shaft needs to be shortened and you use a friction disc for the different splines.

bbundy

Yea when I get back to it Im still needing to work out the details on how to do the swap and what will work. The input shaft sticks out about 1" longer the output shaft is about 1" shorter and both are different splines than a Miata but I don't think that is a show stopper yet. It might be that an FRS/BRG transmission is a better starting point. it basically has the same ratios as the S15.

emilio700

iTrader: (3)

With as many totaled 86's that are showing up in salvage yards, it might actually be easier and cheaper to find one too.

Midtenn

iTrader: (15)

Has anyone looked into making a cradle or similar mount to the one shown to adapt other transmissions to solve the issue of loosing the PPF. The one shown below is from a SR20DET swap kit into the Miata using the Nissan 5spd. I am not saying that is the optimal gear setup, just an idea of an adapter.

miata2fast

iTrader: (2)

That is actually a pretty good idea.

Personally, I am thinking of building my own PPF / Torque arm hybrid to attach to a T-5, but still have a transmission cross member.

bbundy

S15 transmissions imported salvage from Japan are around $400. so far the FRS/BRG/86 ones I've seen are over $1000.

The engines on those mount way far forward I guess you can't really stuff a flat 4 partially into the transmission tunnel like you can with an upright inline 4. They don't have the super thick dual mass flywheel like the S15 though so it might be the front and rear shaft lengths from the center section are closser to the miata version. input and output splines I believe are the same as the S15 at least I know the input is. Input splines are an easy problem to overcome though.

Impuls

iTrader: (1)

I don't remember if we hit on it but I know we touched on it.
Honda S2000, Mazda RX-8,-Toyota Altezza,-Toyota 86/Scion FR-S/Subaru BRZ.
Use the same Aisin transmission, well at lease the transmission code.
Non of these are quite the same as ours? Not a single one is swappable?

Something didn't seem right.

ccsc

Miata 6 speed (green) vs Getrag MT82 (blue)

Getrag MT82's 3rd gear could probably be coped with on track, but the .62 OD is just too tall. Muncie 4-speed's 2-3-4 is perfect, but no OD kills that too.

Maybe just maybe it would be possible to take the MT82 4th, and put the driven on the drive position and vice versa, for the 6th gear, and have a .757 6th. You can do that on the old 911/914 5 sp transaxles. Obviously you'd have to buy a 4th gear set and do a trans rebuild, and it wouldnt be as good as the Miata 6th, but way better than the stock mt82

bbundy

Some are very similar and I believe similar enough to build a hybrid transmission out of the parts bin. Others I think like the S2000 and Altezza are radically different. The others along with the S15 Nissan actually have the Identical center casting section as the miata and as I can figure based on tooth counts I believe the miata version has the weakest 4th gear of the bunch. Accept for 6th gear I also think they have slightly better ratios as well they are a little tighter and not as rediculusly low in 1st and 2nd 6th is too high but there are swap options for that gear.

TorqueZombie

iTrader: (6)

Found a bunch of S15 6speed info
S15 6 Speed Transmission for Dummies - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

emilio700

iTrader: (3)

We are talking with a supplier (not PAR, Quaife or BAR) to get 6spd gearsets and steel shift forks for the AZ-6. I'm leaning towards one ratio option close to what Andrew and I posted above, dog engagement, helical gears. Torque capacity would be as close to 400lbs as we could get given packaging constraints. The Stock AZ-6 is nominally rated for about 200lbs. At 300 + the lifespan gets measured in hours, 400+ measured in minutes.

Target gear ratios, or something near this
2.8
2
1.52
1.22
1
.87

We would have to get about 20 orders. Ball park is about $3100 for the parts kit.
ETA would be roughly 10 months from green lighting the project to you door.

Dog box allows for greater strength but is only happy when banging through gears. Shifting slow on the street can be a PITA. For those that have never clutchless shifted a close ratio dog box, it's only slightly less awesome than a full sequential.

Thoughts?

Leafy

iTrader: (1)

What 2nd gear ratio. Please for the love of Jesus have it be no higher than 2.7, 2.00 or 2.10 would be excellent.