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Old 03-10-2014, 11:06 PM   #141
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Quote:
Originally Posted by Savington View Post
I said that factually, not to be an *******. Sorry if it was taken wrong.



In my opinion, a longer rear end ratio does not adequately compensate for having the wrong ratios. If the ratios are too far spread apart, you just go slower - end of story. Whether that speed loss comes from losing a useful gear which cripples you in slow corners, or whether you change the rear end and end up with an overdrive so tall that you can't pull it, you go slower. There's no "fix" for that, just like there's no "fix" for not having enough horsepower, not having good shocks, not having enough tire, or two dozen other things. You can still go fast, but the guy with the correct gearbox is going to be faster.
Obvious statement is obvious. I get the basic principle. Until someone pulls out the magical transmission out of their ***, everyone will have to learn to make due with what we have available. In the meantime, we will all have to make due with what we have, and learn to make the best of it.

Sometimes, the correct final gear change would be to go lower and not higher. Sometimes that final gear change will cause either a higher or lower gear in the transmission to be the right gear for that turn you are struggling with. Sometimes changes in motor strategy will make the transmission you are stuck with work better. Sometimes.... Do you see where I am coming from?
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Old 03-10-2014, 11:16 PM   #142
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Originally Posted by miata2fast View Post
Obvious statement is obvious. I get the basic principle. Until someone pulls out the magical transmission out of their ***, everyone will have to learn to make due with what we have available. In the meantime, we will all have to make due with what we have, and learn to make the best of it.
There are bad options out there today. A few guys have done the TII swap, and you can buy an off-the-shelf bellhousing from Lakewood to put a T5 box behind a Miata. To use your phrasing, we're literally trying to pull the magical transmission out of our collective *** in this thread, good sir

Quote:
Sometimes, the correct final gear change would be to go lower and not higher. Sometimes that final gear change will cause either a higher or lower gear in the transmission to be the right gear for that turn you are struggling with. Sometimes changes in motor strategy will make the transmission you are stuck with work better. Sometimes.... Do you see where I am coming from?
Trust me, I do - I went from 4.30s to 4.778s and stopped using 2nd gear in my PTE car last year to achieve the same thing (using 3-4-5 instead of 2-3-4), and to make up for the "long" 3rd gear, I built a motor that made peak allowed class power (not torque, but power) across nearly a 3000rpm range. There aren't a lot of stock-cam BP motors that can lay down 145wtq dyno plots, but that motor could do it on pump gas. So yes, I'm intimately familiar with making compromises to work around inadequate gearing. That works for a 140whp PTE car that can't use a 6-speed because of the ruleset, and never needs to be able to go faster than 130mph, but it's not going to fly for a no-rules 400+whp turbo car. If the ratios are too wide, you either lose a ratio entirely by going lower with the rear end, or you can't pull the tall gear if you go higher. Turbo motors (at least the ones I build) are already built to maximize the torque band, so there's nothing left on the table there to pull from in order to make up for the transmission's inadequacy.

Long story short, the 6-speed ratios are sublime on track, I know they're faster than the 5-speeds, and I'm just not willing to lose them in order to make the transmission more robust.
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Old 03-10-2014, 11:25 PM   #143
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If the six speed ratios are so good why is no one trying to organize a custom gearset? There seem to be quite a few people looking for something like that and I'd imagine with some effort and backing from prominent members of the community we could actually get enough people together to make it feasible.
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Old 03-10-2014, 11:44 PM   #144
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Originally Posted by Savington View Post
5mins of google says the 540i's 6-speed (Getrag S6S 420G) was also used in the 740i and the E39 M5, which bodes well for strength for us. No parts available from Getrag, though, and they are known for breaking shift linkages.
Yeah I read that too.
But it seems that Getrag has made approximately a million different transmissions and they are mostly quite stout, light, and have non-retarded ratios and some are really cheap.

Furthermore, unlike transmissions originally designed for v8s (e.g. all Tremec options), the BMW trannies will actually take 8000rpm.

I just want to know if they feel good and which one of them have a removable bellhousing.
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Old 03-11-2014, 12:01 AM   #145
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Originally Posted by soviet View Post

Furthermore, unlike transmissions originally designed for v8s (e.g. all Tremec options), the BMW trannies will actually take 8000rpm.
My biggest fear with the T5.

I think that G Force may have solutions for that, however I have not inquired about it yet. The T5 is my greatest hope to solve my transmission problems. To me it seems to make the most sense for what I am doing.
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Old 03-11-2014, 12:25 AM   #146
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Yeah, the T5 is probably the best bet out of the Tremec trannies. But even the best g-force set still has a 2.42 2nd gear and its meh. And I think the Lakewood adapter only fits the Chevy T5, if even that.
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Old 03-11-2014, 12:41 AM   #147
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There are also Getrag 260 and 265.
3.83
2.20
1.40
1.00
0.81
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Old 03-11-2014, 02:39 PM   #148
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The engines power curve will play a big role in how critical the gear spreads are. As Sav mentioned close ratios like the factory 6 speed are best. When you are forced to compromise consider the power curve of your motor before selection.

Everyone always refers to "peak HP" numbers. In the real world average HP numbers are much more important. This is why a close ratio box rains supreme

For example a 300whp @8k/ 200whp @5k with a trans that drops 3k between shifts would have 250whp average. Now with a close ratio box that drops only 1,500 rpms the average whp is 275. That's a 10% increase. When class limited HP applies that difference is HUGE.

If the motor had a very flat HP curve up top then the wider gear ratios become less critical. Plot your RPM drop on the dyno chart of the various options and do the math. On my Rotrex car a wide ratio trans will kill performance. On a V8 Miata with a broad power curve it becomes less critical. In fact you maybe faster due to less shifting.

In the end you gotta test, test, test to evaluate the changes.

Last edited by k24madness; 03-11-2014 at 03:30 PM.
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Old 03-11-2014, 03:21 PM   #149
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Miata 6 speed (green) vs Getrag MT82 (blue)



Getrag is found in 11+ Mustangs, holds 700+ hp even pushing a heavy moostang.

Has a shitty shifter with soft rubber bushings, but one could build their own or use a fancy aftermarket one. Its also a remote mounted shifter so you would have some freedom to put it where you wanted.

Doesnt like the cold. 2nd gear will explode if you force it in without letting it warm up like an old Ferrari. Gotta double clutch, not granny shift.

Might be too big for transmission tunnel.
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Old 03-11-2014, 03:30 PM   #150
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According to Getrag, the mt82 is a truck transmission, lol
"Rear Wheel driven light duty trucks, Sports Utility Vehicles and pick-ups"

http://www.getrag.com/media/products...TI500_MT82.pdf


There is a 6MTI300 which is ligher duty (350nm or 250ft/lbs rating) but its 33kg or 72lbs dry!!111one
http://www.getrag.com/media/products...00/6MTI300.pdf
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Old 03-11-2014, 03:31 PM   #151
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6th and 2nd both look significantly less than optimal.
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Old 03-11-2014, 03:41 PM   #152
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its also like 110lbs dry
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Old 03-11-2014, 03:46 PM   #153
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Miata 6 speed (green) vs Muncie M22 4 speed



Muncie is straight cut, loud as ****, borderline indestructible beast.

Close ratios with super long first and no overdrive gear(s).

Still being made with custom ratios available.

The manliest tranny. Not for boys.
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Old 03-11-2014, 03:54 PM   #154
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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.
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Old 03-11-2014, 04:44 PM   #155
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Quote:
Originally Posted by soviet View Post
its also like 110lbs dry
I don't think anything with the required torque capacity will weigh much less. Even the 85lb Miata AZ-6 has fragile aluminum shift forks to lower it's weight from the steel fork 95-100lb variants in the Altezza , Skyrine et al.
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Old 03-11-2014, 05:29 PM   #156
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Looks like the AP1 S2000 trans had some pretty close ratios.



Not sure on the strength though. I know there are some super fast s2000 drag cars, but the same can be said for civics and they do not have strong transmissions. Its all just preload and letting the tires spin to keep them from breaking.
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Old 03-11-2014, 05:35 PM   #157
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Originally Posted by Full_Tilt_Boogie View Post
AP1 S2000 trans
S2000 trans is an Aisin AZ6, which was also found in the Rx8, the JDM Lexus IS200, the Nissan Silvia S15, and.... the Mazda Miata.
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Old 03-11-2014, 05:49 PM   #158
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S2000 trans is an Aisin AZ6, which was also found in the Rx8, the JDM Lexus IS200, the Nissan Silvia S15, and.... the Mazda Miata.
^this.
Why can stock s2000 transmissions handle 400-600hp trashing but the miata's can't? Though I understand at 400hp those S2000s only make 290-350ft/lbs.

What's so different internally besides ratios?

Also isn't it in the new GT86/FRS?

Let's all just run powerglides :P
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Old 03-11-2014, 05:51 PM   #159
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the s2k tranny is the most different of the AZ6's. The outer case in no way resembles the rest of them, and the later ones have carbon fiber synchro's. It also shifts amazingly.

The toybaru does have the AZ6 as well. Are there any roadrace ones making crazy power now? I stopped paying attention to them.
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Old 03-11-2014, 06:01 PM   #160
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Quote:
Originally Posted by emilio700 View Post
I don't think anything with the required torque capacity will weigh much less. Even the 85lb Miata AZ-6 has fragile aluminum shift forks to lower it's weight from the steel fork 95-100lb variants in the Altezza , Skyrine et al.
Getrag 265 is, somehow, 100lbs, presumably.
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