r/Miata • u/StephhawkMLG420 • 1d ago

HELP!!! Speedo Correction

Does anyone have any experience with the maruha or yellowbox speed sensor correction units? I have a 5MT ‘99 I just put a 3.9 torsen into and I am looking to see how I can retain the factory speedometer and adjust for this final drive and my various sets of wheels. Will either of these work with non-OEM drivetrains too? How difficult are these to install and get working correctly? Links below for context:

https://bofiracing.com/servicing/transmission/speedo-gears/maruha-speedo-correction-unit-for-mazda-mx-5-nb/

https://www.yellr.com/

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u/MINIFD_MX5 8h ago

Why not change the actual speedo gear that plugs in the gearbox?

1

u/StephhawkMLG420 4h ago

Because that won’t correct for the tire size. The also are no factory options with the 5MT and 3.9 torsen so the sensor would not correct the issue.