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Transmission/Diff Input on Upcoming Swap
Need some transmission/diff input. I have a '01: 5 speed, sport brakes, and an lsd (i believe is a 4.3). We compete in wheel to wheel with it, and will be continuing to take it on the One Lap of America for the next two years. We will be doing the new K24z3 swap, and will likely need to detune it just a bit for wheel to wheel competition, and run it all out for the OLOA. We're trying to figure out what do to about the transmission and rear diff. As is, 2nd is a touch too short, and it screams at highway speeds. We want things to be as reliable as possible, but saving money would be nice too. So what do we do? -would the stock 5 speed be able to stand up to the constant abuse and the occasional hard launch from the new-found power? -go bmw trans and don't worry? -other options? Here's what we would like:
LMK! |
What do you plan to have your rev limit set to?
If it were me, I’d look at a nb6 speed transmission with the 4.3 diff and treat 3rd gear as second and forget that 1st gear exists. |
tbh i'm not sure what those motors can reliably do...
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The 6 speed has a lower top gear so worse. The 5 speed is vastly superior in weight and feel if you are racing. You may want to pair it with a 4.1 for the distance and giving you better gearing in 2nd for autocross.
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Originally Posted by sixshooter
(Post 1545323)
The 6 speed has a lower top gear so worse. The 5 speed is vastly superior in weight and feel if you are racing. You may want to pair it with a 4.1 for the distance and giving you better gearing in 2nd for autocross.
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For OLOA I would be worried about the longevity of the 5 speed behind a healthy K24. There is a lot of conjecture around what causes them to break and around how to fit it, but they still break, a lot.
If I were going to take a 5 speed car with any real power on a OLOA "Excursion" I'd make sure I had one spare with me, I had practice changing it, and that I identified junk yards near the route who could have spares along the way. |
Gearing Calculator - Graf Garage Play with gearing to your hearts content.
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I assume you will be using KMiatas swap kit. Maybe give considerations to also doing their BMW trans swap.
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Originally Posted by Your Drunkle
(Post 1545464)
I assume you will be using KMiatas swap kit. Maybe give considerations to also doing their BMW trans swap.
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6sp + 4.3 + earplugs
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Haven't heard of ecotecs killing 5 speeds, I doubt the z3's will either. I have about 7 years of track (HPDE, but still) and street miles on my 5 speed making 220whp. Zero issues.
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Originally Posted by TNTUBA
(Post 1545338)
For OLOA I would be worried about the longevity of the 5 speed behind a healthy K24. There is a lot of conjecture around what causes them to break and around how to fit it, but they still break, a lot.
If I were going to take a 5 speed car with any real power on a OLOA "Excursion" I'd make sure I had one spare with me, I had practice changing it, and that I identified junk yards near the route who could have spares along the way. |
I think a lot of those turbo guys aren't doing multiple hundreds-of-miles road trips with repeated track events between them. After 10yrs of playing with Miatas it's just plain annoying to me when people suggest a 5-speed for anything related to track use. They are weak and they're objectively slower than a 6-speed in the exact same car. Period, end of story. Anyone who says otherwise is wrong.
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Originally Posted by Savington
(Post 1545765)
I think a lot of those turbo guys aren't doing multiple hundreds-of-miles road trips with repeated track events between them. After 10yrs of playing with Miatas it's just plain annoying to me when people suggest a 5-speed for anything related to track use. They are weak and they're objectively slower than a 6-speed in the exact same car. Period, end of story. Anyone who says otherwise is wrong.
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Originally Posted by Savington
(Post 1545534)
6sp + 4.3 + earplugs
Originally Posted by apexanimal
(Post 1545965)
any input as to the rear diff? i'm really split between the 4.1 and the 3.9 with about 200hp... i'm tempted to do the 4.1 to keep the better acceleration on track, but not sure if the 3.9 will be fine or not...
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Originally Posted by apexanimal
(Post 1545965)
any input as to the rear diff? i'm really split between the 4.1 and the 3.9 with about 200hp... i'm tempted to do the 4.1 to keep the better acceleration on track, but not sure if the 3.9 will be fine or not...
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Originally Posted by Savington
(Post 1545971)
4.30s at minimum. Maybe even 4.44s with only 200whp/160tq. You need to rev the snot out of that thing, constantly, to get it to work.
we've already got hearing protection... it gets rough in there. |
It's a race, you're driving a race car, I'm unsure of what you expected when you got yourself into this mess. I doubt anyone will be able to hear your tiny violin over the sound of the 3" exhaust attached to the K24. In short, sack up :party:
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WHAAAAATTT???? DID YOU SAY SOMETHING???
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Originally Posted by Savington
(Post 1545978)
It's a race, you're driving a race car, I'm unsure of what you expected when you got yourself into this mess. I doubt anyone will be able to hear your tiny violin over the sound of the 3" exhaust attached to the K24. In short, sack up :party:
doesn't mean i can't be idealistic from time to time. it's the balance we're trying to strike between on-track performance vs a significant amount of transit driving - while towing a trailer. it's far less about the noise, because we've been dealing with that, and more about trying to have some mechanical sympathy on this car during the transits - which is when most of the oloa cars break. the 4.3 isn't going to fly with the 6spd as long as we're doing the oloa. but you all have convinced me that the 4.1 will be a better performance ratio than the 3.9 even if it costs a bit on the transits. |
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