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FD gearbox strength

Old 11-13-18, 06:54 AM
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Question FD gearbox strength

Hi there.
I don't have an RX7 but i am considering using the FD gearbox to fit in a retro car (engine turbo Honda K24). I was wondering about how strong the standard gearboxes are.
The plans are for no more than 400bhp and i won't be running tyres any wider than 205. I'm not into hard launches (drag) although i do like a bit of gymkhana and drifting.

The Toyota R154 and the RB25 boxes (expensive) are also an option, but i saw that the RX7 FD boxes were a lot cheaper.

Do you think this gearbox would hold up to the power? Any better suggestions?

Thanks
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Old 11-17-18, 09:21 AM
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the FD people seem to break these transmissions at around 450lbs/ft in 3rd gear, give or take. this is in a ~2700lbs car.

you might have a look at the gearing, its ok for a car with a low flat powerband, but if you build something peaky, it sucks donkey *****
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Old 11-17-18, 09:52 AM
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Thanks for the reply The car will be a lot less than 2700lbs, around 2000lbs. So that should help stress the gearbox less and with maximum width 205 tyres on the rear, it sounds like it could be strong enough and not have to worry about it breaking.

Comparing the ratios of the Honda Integra DC5 with the K20 and a 4.3 final drive.

FD ------------- K20
1st 3.484 ---- 3.266
2nd 2.015 ---- 1.88
3rd 1.391 ---- 1.121
4th 1.000 ---- 0.921
5th 0.806 ---- 0.738

They don't look too far away... Maybe playing with the final drive would be an option.
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Old 11-18-18, 02:25 AM
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In a lighter car with smaller tyres it should be ok.
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Old 11-20-18, 03:10 AM
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Yeah, thanks for that... I can now start buying the necessary parts
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Old 11-29-18, 08:33 AM
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Should be ok but the adapter plate to a FD trans will likely eat up some of the cost savings.
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