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Rear gear for turbo and th400, juat swapped from M6

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Rear gear for turbo and th400, juat swapped from M6

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Old 07-11-2018, 07:39 PM
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Default Rear gear for turbo and th400, juat swapped from M6

Trying to figure out what gear I need now. I am coming from an M6 and it has 3.42s in it and now feels like it's goin to run out of gear before the 1/4 mile is up. I'm on a 26 inch tire and will probably stay there. What gear should I go to give me some more up top without going too much the other way?
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Old 07-11-2018, 08:05 PM
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Maybe a better question would be what mph at what rpm will the th400 get me with a 26 inch tire and a 3.42 that I have now? Feels like it will max out around 130 or so.
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Old 07-11-2018, 10:07 PM
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What rpm you running through the traps? 6000rpm should be about 135, going to a 28" tall tire would get you another 10mph at the same rpm.

http://www.crawlpedia.com/rpm_gear_calculator.htm
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Old 07-11-2018, 10:10 PM
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Originally Posted by biketopia View Post
What rpm you running through the traps? 6000rpm should be about 135, going to a 28" tall tire would get you another 10mph at the same rpm.

http://www.crawlpedia.com/rpm_gear_calculator.htm
I haven't run it yet but I'm anticipating this car trapping mid to upper 140s and don't want to spin it 7000 rpms but also don't want it to be lazy out of the hole. It will mostly be a street car though.
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Old 07-11-2018, 10:12 PM
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That calculator you posted said I would be at 6630 rpms at 150 mph so that isn't too bad if it's correct.
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Old 07-12-2018, 06:27 AM
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Should be pretty right. I tired a few just to self check as it's been awhile since I was playing around with gear ratios and such. What size converter you running to help it get up in the power band?
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Old 07-12-2018, 06:50 AM
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Originally Posted by biketopia View Post
Should be pretty right. I tired a few just to self check as it's been awhile since I was playing around with gear ratios and such. What size converter you running to help it get up in the power band?
It's a 10 inch converter but I don't know all of the details about it, I'm waiting on Dalton to email me back with the specifics of what he speced out for me.
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Old 07-12-2018, 06:52 PM
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Well I decided to go to a 28 inch tire and keep my 3.42s and see how it goes. With a 28 inch tire it looks like I will be turning 6150 rpms at 150 mph so that is tolerable for now. If I needs a little more rpm for highways pulls I'll switch to 3.08s but and hope it doesn't kill my launch.
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Old 07-13-2018, 05:44 AM
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I would think you'd be ok with what you have. Hopefully your converter is set up right to jump you into building boost pretty easily.
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Old 07-13-2018, 09:10 PM
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Originally Posted by biketopia View Post
I would think you'd be ok with what you have. Hopefully your converter is set up right to jump you into building boost pretty easily.
Hopefully so, I'll know for sure next week when the rims and tires get here.
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Old 07-22-2018, 04:16 PM
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What is the engine and turbo size? Your launch shouldn't be a problem at all.
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Old 07-22-2018, 04:20 PM
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Originally Posted by rpturbo View Post
What is the engine and turbo size? Your launch shouldn't be a problem at all.
It's a 408 with a Borg S480, 96 mm turbine, 1.25 AR.
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