Gearbox options/experiences
#141
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.
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.
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?
#142
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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?
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.
#143
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.
#144
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.
#148
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.
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 02:30 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.
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.
#150
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
"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
#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.
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.
#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.
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.
#159
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.
The toybaru does have the AZ6 as well. Are there any roadrace ones making crazy power now? I stopped paying attention to them.