How this idea? 20B + RX8 Transmission

[Glass Machine]

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?


Hope you guys are having fun.

[TitaniumTT]

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"

[RETed]

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

[TitaniumTT]

Originally Posted by RETed

No.

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


-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

[djmtsu]

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.

[reddozen]

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.

[RETed]

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

[Chibana]

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).

[TitaniumTT]

Originally Posted by reddozen

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.

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.

Originally Posted by RETed

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.

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.

Originally Posted by RETed

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???

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.

Originally Posted by RETed

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..

.

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

Originally Posted by RETed

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...

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.

Originally Posted by RETed

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

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.

[Rotary Inspired]

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.

[TitaniumTT]

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.

[project86]

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

[TitaniumTT]

Oh I will 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.

[RETed]

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

[Rotary Inspired]

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.