I was just browsing and the idea popped into my head "hey i wonder if it would be possible to put an rx8 transmission into my SA" The only reason i would consider doing this is to maybe get a little better gas mileage out of my SA. The reasoning behind that is that being that the rx8 tranny is a 6 speed...that extra gear would increase gas mileage by lowering rpm's.

What do you guys think? would it be possible, and if so logical?

 

Well, it may be doable. You would need to see if the shifter lines up (the FBs and 2nd gens have the shifter further back than the SAs, not sure on the 8). 2nd prob is that the RX-8 tranny has no output for your speedo. 3rd, the 6th grear isn't much different than 5th on your car (.84:1 on the 8 according to what I found). The 6 speed may have higher rpm on the highway than your 5 sp (I didn't look up your gear ratio, but it is probably .78:1 or so. I can't remember off the top of my head. The advantage of 6 speeds is you have an extra gear, so the gears are typically closer together. One more disadvantage of the RX-8 tranny is it has been shown to be weaker than a lot of the 5 sp.

On the gear ratios, what I am saying is 5th on the 8 is the same as our 4th. 6th on the 8 is like our 5th.

 

personally, it wouldn't seem to be worth the hassle, but it's your car. i'd really be interested in any data you collect though. another factor to consider in all of this is the great difference in wheel size, so the numbers would need some adjusting, no?

 

a lot of trouble, time, and money.

a better idea would be a FC NA tranny, but it also isnt a good idea for a 12a. the 12a wont have enough torque for the longer 5th. the stock 12a tranny or a SE tranny are the best options. if youre boosted then the FC tranny isnt a bad option.

you can easily pull 25+ mpg on a stock 12a tranny.

 

gear wise the 2nd gen na tranny would be a better choice than one of the two se trannys. yes there was 2 differant gear sets in the se's. the shifter location Is just a little differant than the first gens other wise bolt in for the second gen tranny. the rx8 trany will take a lot more work and in addition its a weak problem tranny thats not even a mazda tranny. 12a tourque would not be a issue.

 

that particular extra gear will not lower your rpms. just because its a 6 speed, doesnt mean its a double overdrive like an american car, its not.

however, if you're gonna put an rx8 trans into an rx7 the SA is the easiest. the rx8 shifter is further forward than the FB/FC, shifter would be really close to lining up in an SA body.

you need a t2 clutch/flywheel.
rx8 starter
t2 style driveshaft

and a custom trans mount, as the rx8 uses a power plant frame and doesnt really have one

 

Ya I agree with you guys, might be too much trouble. Oh well, just a thought. Thanks for the input guys

 

Hmmm... What other transmissions could you mount in an FB (regardless of engine, so be it 12A, 13B, Renisis) that would line up and provide a 6th gear?

A Welding industry friend of mine said he knew a company that makes custom adapters for engine/trans, was making a custom car with his dad so he needed one, and we started talking... well you know how it all goes.

So opinions on effective transmissions with a good 6th gear would be interesting to get and look into.

 

Even better idea. Just get a RX-8 shift ****(same threads as the SA shifter),and tell everyone you have a 6 speed in the car. I really don't think it is worth the hassle,but then again I like my SA just the way it is. I don't even care about gas mileage,but then again I don't drive it everyday.

 

I remember reading about a unit that mounts inline with your drivetrain,it kinda looks like a transfer case for a small truck or something but it adds 3 gears to any car you can mount it in,so on a 5spd car you get it in fifth and wind out then the unit starts,you wont need a clutch for it to shift then it is like an auto when you get into it,I'm trying to find it...I'll try to post pics.

 

Greater numbers of gears is not necessarily better, in every case. You have already the option to change ratios now. RX-8 engines and are not identical to SA engines, and the RX-8 weight is greater. When you alter the torque and power characteristics of your engine, again the gear ratios can be evaluated. To ask only for another transmission or another gear is simplistic, without asking the question where each gear ratio should lie in the Powerband.

 

I don't think the RX-8 gears are much different from the SA gears.

They are very similar untill 4th gear. You may get a half of a mile increase but hey, in the long run it's worth the money savings.