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Old 06-06-2017, 12:15 AM   #1 (permalink)
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Civic VX wrong RPM (tachometer) readings, or wrong transmission?

I just bought a new (used) white VX, and it appears that the tachometer readings are not what they should be.
According to the majority of posters that I read on this forum, the RPMs in 5th gear should be ca. 1000 at 30 mph and 2000 at 60 mph.
My readings are: ca. 57.5 at 60 mph, and proportionally slightly higher RPMs at every speed, compared to what they should be.
I verified the speed independently with a GPS speedometer. The speed readings are correct.
It looks like the car is all stock, therefore I would find it unlikely that the transmission was replaced with a wrong one, or modified.
My question is how would I verify that the car has the correct transmission (P20)? Where would I look for the transmission?
Also, is the rumor true that there are possibly different versions of "P20" transmission with slightly different gear ratios?
Is it possible that the tachometer is slightly miscalibrated. so as to show just an ever so slightly higher RPM at every speed, but otherwise behaves normally?

On another note: I have another (blue) VX, cluster works perfectly and speedometer and tachometer work smoothly. On this blue VX, the the RPMs are 1000 at 50 mph and 2000 at ca. 65-67 mph. I have not yet verified the speeds independently on this one. I read in an old thread on this forum that this behavior is not possible, as there is no longer great ratio on any alternate transmission that would physically fit the VX than the stock VX transmission. Can someone confirm this?

On yet another (red) VX of mine, the speedometer is broken, and the tachometer is way off high and low in irregular patterns.

Is is possible that the tachometers are just not really high quality on the Civic VX, and usually either break or get miscalibrated at 100k+ miles? What are your experiences?


Last edited by comegetme; 06-06-2017 at 12:23 AM..
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Old 06-06-2017, 08:21 AM   #2 (permalink)
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On this blue VX, the the RPMs are 1000 at 50 mph and 2000 at ca. 65-67 mph

If rpm's are 1000 @ 50 mph in 5th then 2000 rpm's in 5th gear would be 100 mph.
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Old 06-06-2017, 11:05 AM   #3 (permalink)
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Right tire size?

Anyone messed with the instrument cluster? Ie pulled the needles off to install aftermarket gauge faces?

Could be an electrical issue. Corrosion, bad/weak ground, yada yada.

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