Who's done it and what is the preferred transmission of choice?

Driving a more modern car (s2000) really ruins you when you go back to your old tired tranny . The rx8 tranny seems to be notoriously fragile but is theoretically the easiest to swap. The s2000 transmission can handle more power but would require some custom machine work to make it fit, and it leaves you with a pretty useless 6th gear.

Looking to swap into an FC chassis with an NA engine. The stock 5speed feels like it has the worst ratios in the world after driving modern equipment. Has anybody bothered to swap in a 6th gear and if so what transmission was selected? Is it worth the trouble or is changing the final drive and running tiny tires the better way to go?

 

rx8 tranny will hold fine for NA power

 

^ what he said.
find an S2 trans from the 09+ rx8

 

Would swapping the transmission require changing out the clutch and flywheel as well or do all 13b engined cars share the same flywheel dimensions? What about the throwout bearing/pressure plate situation?

 

IIRC you need to change to a turbo flywheel/clutch setup, then get an auto driveshaft or have one made

 

Rx8 trans requires the T2 clutch, and starter. not sure about the driveshaft, it is turbo diameter, but i think the length will be different. biggest hurdle to Rx8 trans is that the shifter is further forwards.

there is/are some factory parts to move it to the correct location for an FC, but i'm not sure what they are. possibly the 6 speed miata trans, from 99-05 in the miata and 04-08 in the Rx8 they both use an Aisin trans (its related to the S2000 trans). the 09+ Rx8 trans is a Mazda design.

the trans mount needs to be fabbed, although there are big studs on the trans, so it looks pretty simple.

the Rx8 trans has no speedometer drive either, so that is a consideration.

 

Maybe just swapping in the miata gears into the FC box might be "easier"? I have a spare s4 trans I could butcher for the experiment and keep the rx7 5th gear. It should be pretty easy to find the needed miata parts.

I just find the stock gearing obnoxiously long for such a low powered car. First and second are fun, third is already a bit of a stretch, and fourth is completely useless. Third is the ticket for overtaking at highway speeds so I don't know who fourth is supposed to be pleasing.

I'm sure a turbo would "fix" my gearing complaints but that's not the point

 

Some of the higher-power owners, myself included, either have or are swapping to T-56s as the gearing is complementary to a wider powerband. Since mine is set up to be in the fun zone from 1800rpm to redline (because 20B and twins lol), I opted for a LT1 T56 out of a 97 Camaro. Yes, acceleration will probably be slightly stunted off the line (2.66:1 1st gear) when compared to the Infini IV transmission I currently have (3.475:1 1st gear), but the benefits FAR outweigh this minor annoyance. It's a stout piece, known for being able to handle plenty of high power abuse, parts are easily available from plenty of sources and custom gearing can be done if one desires. I'm staying with the stock LT1 ratios because its 6th gear is downright beautiful for road trip cruising...0.5:1

 

I'm currently working on a MT82 Getrag 6spd adapter plate for rotary. I'm going to make one, try it in my car or a close friend's whose is at my house, and once I have definitive info that all is good to go, I'll post up pricing. All of this is for my 4Rotor REPU project, but if others find it desirable, then great.

The MT82 has been proven to hold upwards of 700+hp and loads of V8-With-Sticky-Tires-On-A-Drag-Strip-Torque, but only after Bronze shift fork pads have been put in. A worthwhile upgrade that would give you a 6sped Getrag for less than a Supra trans or T56.

I'll keep everyone posted.

 

I run a series 1 rx8 trans on my rx3. Big street port NA 13b with a 4.44 rear gear... no issues so far... always in my powerband, I love it!

 

I have a walkthrough on how to rx8 gearbox swap in my build thread (see link in signature) however a lot of the photos are missing but the details are right.

fab mount is easy, the rest is some just a new honda slave cyl from autozone, 2 alternator spacers, longer bolts for the bellhousing and you have to cut the floor slightly which can be no big deal if you have a racecar but if you don't well its kind of a PITA.

I think you can use the driveshaft as is but I shortened mine .75" to avoid any binding which is also a good opportunity to freshen up the ujoints which are probably ancient.

 

[QUOTE=73rx313b;12297163]I run a series 1 rx8 trans on my rx3. Big street port NA 13b with a 4.44 rear gear... no issues so far... always in my powerband, I

hey mate looking at installing a rx8 s2 6 speed gear box in my Rx3 coupe would love to speak and discuss how the fitmant is as I think I’ll come into to some shifter postion issues could you please contact me to discus

 

[QUOTE=James Sioris;12343438]Keep in mind the ratios in the S2 6-speed are different than the S1 as they also went to a 4.78 rear end ratio on the S2 (S1's were 4.44).

 

have one in my vert. love it

 

I just picked up an s1 6-speed trans for my 79 with streetported s5 4-port NA. I have a T2 trans installed right now but not happy with the gearing. For those who have the rx8 trans, what did you do about the speedo?

 

use rpms to judge speed, 4k in 6th is about 80mph, same as rx8

 

There are several options for the speedo issue but the best one in my opinion is a Speed Hut GPS speedo. That just makes is easier if you want to change a rear gear ratio or tire size. I looked at a Cable X which would work fine but you would need some sort of speed sensor. The Cable X will allow you to keep your factory speedo and cable system.

 

Pretty darn close but it will also be affected by your wheel/tire combo too. Since my car is an rx3 and 15's are about the max without body mods. Its not really off but maybe 300rpms maybe

 

Any update on the 82 trans ?

 

A US race trans shop is working on upgraded gearsets for the NC MX5 and S2 RX8 (2009+) 6spd transmission. The price they estimated was fairly reasonable compared to the other gearset options offered overseas.
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