How this idea? 20B + RX8 Transmission
 

We know that when you put a 20b in a seven you end up messing with your 50/50. If you want to keep that 50/50 have to move the motor back in to the firewall just a little bit. When you do this you obviously are also moving your transmission back so the shifter is now moved back also and in a uncomfortable spot and well who want to be uncomfortable when your driving. right?

So my idea is use a RX8 transmission, I was told it was about 6in shorter then seven trans. (correct me if i am wrong on this) that is about as far as you would need to pull the 20b in to the firewall to keep your 50/50? So in theory you can keep your 50/50, have the the shifter in the same comfortable spot and you have a 6 speed to play with to boot.


One more thing, anyone know if anyone has done a 20b-Renesis yet? :beatdeadhorse5:


Hope you guys are having fun.
:cheers2:

Not a new idea... I just suggested it to a potential client a few days ago when talking about his 20B FC. It's not 6" shorter, it's 3.625" shorter and it's only the shifter location. The overall trans length is within 1/2"

No.

The RX-8 trans cannot take the torque from a modded 20B...especially turbo'd.

I think 50/50 weight distribution is overrated.
Remember, it's STATIC weight distribution, which means it doesn't really mean jack when you're driving around the track.
DYNAMIC weight distribution is almost impossible to nail down, but this is the number you want when you're driving.

Side note, we got no problem tracking our 20B FC just by messing around with the stabilizer bars.


-Ted

No one knows how much torque an RX8 tranny can hold because I've NEVER heard of one blowing up from torque application. Every person that I spoke to had the clutch depressed and thier foot off the gas when thier tranny puked

Everyone talks shit about the RX-8 trans. Mine has 198000 miles on it, original, and shifts perfect and makes no noise. It is all in how you drive the car. If you are banging into gears with reckless abandon, and trying to be the drift king, then yes, it will fail. But just driving aggressive, and knowing HOW TO SHIFT will make it last a long time.

People say the same thing about the NA trans behind a TII. I had zero issues, and I always drove aggressively, and tortured it on the Dragon 3 years in a row.

I'm with ted... Renesis trans is a bad idea. Not to mention the gear ratios are better in the jspec T2 trans anyway. If you're really insistent in "50/50 balance" then find someone local with a corner balancer and add weight to the ass end. That's what I would do rather than use a weak transmission. There are several threads on the RX8 club forums detailing all the weak parts and how / why they fail.

It's really a matter of physical limitations here...
With helical gear transmissions, stronger gears are a matter of making the gears wider.
You can get an idea of the strength of the transmission by looking at the length of the gear case itself.
Now, keep in mind that if you're looking at a 6-speed transmission, you're stuffing another set of gears for that extra gear over a 5-speed transmission.
So unless the RX-8 is using some different cut gears (dog cut gears) or exotic metals (highly doubtful), how does it's 6-speed transmission - which about the same length or slightly shorter than a 5-speed FC turbo / FD gear box - have stronger gears???

Rumor has it that the RX-8 6-speed transmission is a variant of the Miata 6-speed transmission.
Now, I can't confirm this, but it makes sense for Mazda to do this just to keep parts costs down...

So, go ahead and try and use that trans behind something putting down - at least - 300 easy pound / feet of torque at the flywheel and see how long it lasts...

Now, with that said and done...
Yes, if your shift technique is "delicate", you can minimize wear & tear of the transmission.
I do not doubt claims of extended mileage on these transmissions.
I do question why you would want to put it behind a 20B project?
Why not just stuff a non-turbo FC transmission behind a 20B if you're going to argue otherwise, since these transmissions are basically free for the taking?
There's "possible" and then there's "not recommended".


-Ted

I have no opinion on this discussion as I have no knowledge of 20b swaps, but I can say for sure that the Series II (2009+) RX-8 transmission is from the MX-5. It was my (possibly mistaken) impression that it was stronger than the MX-5 version, however. I believe I read that in some of the reviews of the 2009 RX-8. Series I RX-8 transmission is not from the MX-5, but an Aisin transmission (http://en.wikipedia.org/wiki/List_of..._transmissions).

No way man, the ratio's on the Jspec S5 TII trans are ABISMAL at best. The overdrive gear is the same to boot. I HATE the ratios in my trans, they suck.

Not to mention you never want to ADD weight to get a balance.

But the Aisin trans does NOT do this. Gears 1-5 are in the same case and the same length as the Type-R box. The 6th gear is in the extension housing.

See above for the explaination. I've owned or dissasembled or held in my hand gears for all the trans' listed in this thread and I can tell you that there is not a noticeable difference in the size of the gears between any of them.

.

It is, I can confirm it and Flyin Miata has used those trans' to some pretty serious HP levels.

I plan on it, in about a month or so, except I'm making WAY more than that @ the flywheel. i'm putting down 323 to the rear wheels, and I'm NOT delicate. i have every bit of faith in the trans that was "blown" when I bought it for $200 delivered. Every single gear, sync, hub was reuseable. The bearings showed signs of wear, and of course I'm going to have the sync's replaced but I have no doubt that the trans will take the torque that I'm making.

Ted, I understand where you're coming from, but honestly, how can you make such strong rec's based on internet research? Have you ever dissasembled an RX8 trans before? Compared it to FD/FC and miata gears? I have, and I built a trans that bolts in with some MUCH better ratio's than the craptastic mack truck shifting S5 TII box.

Go check it on 8 club. There were several (2 i know of) who went through 8 trannies like they were underwear behind their 20B in the RX-8. There is a reason people have migrated to a T56 behind the 20B.

Good luck in your efforts. I would hate to see someone have to buy several trannies but hey sometimes you have to figure stuff out for yourself.

Without giving away my own efforts, did they address the problem or did they just continue to rebuild/replace trannies? There's nothing "weaker" about the 8 tranny over the others, there is an inherant problem that needs to be addressed.

this has definitely sparked my interest. Brian... since i know you are always testing, keep me posted on what you find :)

Oh I will :D Even if it blows up on the first dyno pull, and I mean REALLY blows up as in the case flex's and the gears sheer teeth, then I will say - yeah, the trans is weak. But if they keep failing in the way that I have ALWAYS seen them fail, then no, I will continue my stance that the trans is just as strong as the others, just built with looser tolerances and an inherant design problem.

Like DJ said though, alot of it is in how the trans is shifter.

Personally I HATE the Type-R box. I hate everything about it. I hate the ratio's, I hate the weight, I hate the fact that it shifts worse than any of the trucks that I've owned. The only good thing about it is it's a known strong box that can take ton's of torque.

Local RX-8 owners have been all blowning up their transmissions, and the local Mazda dealers are tired of dealing with it.
That's basically my "direct" experience with them.
I guess you can argue that the local RX-8 drivers don't baby their transmission...


-Ted

Titanium,

They were just replacing them. I had a 2nd gear grind occassionally on my 8 when I had it w/ the Aisin trans. I have yet to take the Aisin tranny apart so you may know more than me here on the interals, but I haven't had any problems w/ the TII tranny behind the 20B I helped w/ and that is where I make my recomendations. I just can't imagine putting down that much power the added torque the 20B produces and expecting the 8 tranny to hold. It might be better w/ straight cut gears ie dog box, but again I have not tried. I am just going on what I have seen and had a hand in.

What is the inherent flaw? How do you usually see them fail? Also what drive shaft would you use to make this work in the fc? That seems like another obstacle.

When taken as a group I doubt the HI crowd is any harder on their teams than the group in CT
I doubt that they are blowing apart, stripping gears, breaking shafts or anything else that I would co wider blowing up. I bet each tranny could be fixed with minimal effort/parts. Why Mazda doesn't do this I don't know. FWIW the earlier Raisin boxes found in the Miatas were a better design.
Again, its not a strength issue with the trans. I cannot stress this enough, all the failures the I have seems and spoken to owners about have NOT been caused by applied torque. The TII box is more RELIABLE, I'm not doubting that all I am saying is I have never seen a Renni tranny blow up. I've seen plenty of failures but never seen one destruct from torque
Its allowing the 2nd gear hub to over extend itself and jam. Trans doesn't shift and sometimes won't even rotate. People assume.... Key word.... That its blown when in reality its completely usable after disassembly. Stock TII driveshaft with a slight mod should work. I'll update y'all in a few weeks when I get it back.

So this is still a problem even in the newer model 8's? Ill have to be completely honest. It sounds like a pain in the ass. I mean, who wants to have to randomly pull apart their tranny to fix somethin like that? Im still ridin the fence on the subject but if you can convince me it wont be a problem then im cool. I honestly dont have beef with the TII tranny. Although ive only driven one and i only have my honda tranny, NA 7 tranny, and a hyundai santa fe tranny to compare to hahahah:rofl:

As far as I know, yeah, it's still a problem. We're working on resolving it with my trans, which is based off the 8. Honestly though, I despise the TII box, I hate the chunky fucker. The Renni box is much nicer to drive, it's just dealing with that hub and properly limiting the travel. We have ideas and will hopefully be pulling it apart friday. It'll will work, I promise you that. Take a look at the ratio's and tell me that it's not a better trans for any ported engine.

ill give the ratios a looksy. havin a 6 speed would be kinda cool :)

I have an RX-8 with over 85K on the tranny and I've had no issues. I know quite a few people that ran Esmeril Turbo kits or even the Greddys and they've had no issues with the bump in torque. I was talking to Dave at KDR and he said as long as its within reason and you don't drive like a maniac you won't blow through your tranny (same goes with the motor). Him and I have been tossing around the idea of dropping a NA 20b in my car all while using my same transmission. Since I plan on keeping it in NA form, Dave said the RX-8 transmission will do just fine. As far as the balancing goes, you are just better off taking weight off of the front end than you are adding weight on the rear. I didn't think you could move the 20b back 6 inches in the FDs.

I must say I agree with Dave and with your experiences regarding the trans.

You could move the engine 6" back in the FD, you'll just have to cut the firewall out and fab in a new one. Sounds easy right ;)

Now you got me thinking about how much I'd have to cut on the 8 in order to get a proper balance. There was a company that was supposed to make a bolt on subframe. They were trying to go about it two ways, I'll try to copy and paste his website link on here, once I find it. They haven't gotten very far as of yet, and I am hoping they do it soon. One of the ways was supposed to come with a subframe with mounts pushed back and a shortened drive shaft so that the steering rack would remain in the same place. The other was a relocation of the steering rack and something else which I cannot remember.

im kinda startin to like the idea of this though. now that i know its not gonna take some outrageously priced custom drive shaft.

From what I have seen, people who don't know how to shift like a man, but rather a gorilla, are the reason for most transmission failures.

May I present: http://raceroots.com/index.php/produ...cro-saver.html

This should help the retards from overshifting and tearing them up.

bahahahaha... silly retards

Thats actually a cool idea. i like it.

I have one, but never put it on.

looks like it would work well. these guys must really be pounding through the gears though to be doing that damage. I dont know that i would need one of those but it would be a decent preventative measure though. seems over priced...

You can find them on RX-8 club used for cheap-ish.

Any competent shop (cough ahem KDR cough) knows about the problems and knows how to deal with them internally and properly. Mazda even had a TSB on it apparently and sells a different linkage that prevents the over extension.

Well as of now it sounds like there is a firm grasp on the problem and plenty of competent people (cough ahem TTT/KDR cough) and a way to make it work.... dooo itk!

wow, i didn't think it was that much of an issue. How hard is it to not push it further or to fully keep the clutch in until it goes into gear? What is the final drive ratio in the FC/FD? I know the RX-8 has a 4.44 and the second gen has a 4.77. Suppose I did do this swap and kept the stock 8 tranny, would it be fine with the stock 4.44? I think Motortrend had an article where they tested the R3 RX-8 which had the 4.77 gear ratios and they said that other than straight line performance it wasn't any benefit, and that around a track or autoX the older tranny/diff setup was more beneficial and had the right ratios to get the job done.

Pushing it too far is only one issue. It over extends the hub and bing.... The other issue is idiots grabbing hard and the sync not being fast enough, or the force being too hard and the hub tweaks and bing...

Gear ratio's in non auto FC/FD are 4.11:1 with a few exceptions.

What swap? The 20b swap? Yeah, it'll be fine. IIRC the 8's tires are taller as well which nessitated the higher ratio. A Renni tranny in a turbo or ported FC would be about damn perfect according to my math. We shall see though. But for an auto-x, it would be a JOY compared to the TII box. That thing is miserable for auto-x.... I fucking hate it.

Thanks! Last time I saw you at AutoX you were pretty fast. I take it that your ratios are not best suited for that. In most courses I'm in 2nd but I'm just at the lower end of my power. I'm probably around 6000rpms and would much rather be around 7 when all my power kicks in.

Thanks man.

Ratio's definately suck. I'm high in the rev's in 1st.... 1st! And will occasioanly hit 2nd. With the 8 box in my car I can tool around in 2nd with a TON of torque at my disposal. My torque comes on hard ~3500-4k and holds till 7. Anywhere in that range I'm good. With the TII box I'm either high in the rev's in 1st or bogging slightly in 2nd. I hate that box.

Have you ever raced with FCSCC? Their courses are usually a little looser. I gotta get on the dyno and make it back to CART. Are you going to thier Limerock day? As of right now I'm attending, but waiting to see what happens Friday before I pay.

My first autoX was with FCSCC, I really liked them over CART. The courses are a bit faster and not as tight and they're pretty cool about stuff. I'm going to the next FCSCC meet. I'd like to do CART but unless I quiet my exhaust down, it wouldn't be wise for me to show up. BTW, I see whole car part outs on rx8club.com if you want a RX-8 transmission. I'd really like to get a flywheel so that my RPMs cam climb quicker so I'm in my sweet spot more often than not, the only thing is I'm not sure how quickly the revs drop (it may or may not be beneficial as I may lose some mid range torque).

You will only gain torque by freeing up rotating mass. It may feel like you loose torque off the line but the dyno says otherwise. What you feel is the drop in inertia. Less energy stored in a lighter flywheel...

Totally botched the physics but you get it