Tachometer is very inaccurate

[Sn8kebitten]

I’ve had a suspicion for awhile now that my tachometer has been reading off since buying my Cobra back last year. It never felt or sounded the same during WOT like I remembered from 10 years ago. At 70mph with 4.10s, it reads around 3400rpms and even with those gears, that seemed higher than I remember. So I hooked my SCT X4 I have from my other car up to it, and if I hold the gas at what the cluster says is 3000rpms, the tuner only shows 2493rpms. While held at 4000rpms, it showed 3320rpms. Any ideas where I should start to finding the problem? Or should I just try to find a used cluster to swap into it?

 

[adammdennis11]

https://www.cjponyparts.com/speedometer-driven-gear-kit-type-3-17-18-20-21-tooth-mustang-with-automatic-manual-transmission-1965-1998/p/SGK1/?msclkid=06365491241018489a6a32a2541a7868

 

[96dreamer]

Is it possible the needle on the tach was removed at some point? I had to remove mine a while back and it is still ever so slightly off.

 

[venom1997]

It’s crazy I don’t even look at my cluster gauges anymore run a scan gauge 2 Velcro to my dash above the steering column I have it set to read rpm mph iat and water temp it’s easier to view a digital gauge set. However my analog tach is spot on with the ecm rpm I wonder what could cause that other than the needle has been moved at one point by hand. Mwolson would know paging Mwolson


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[Black Gold 380R]

Is it possible the needle on the tach was removed at some point? I had to remove mine a while back and it is still ever so slightly off.

Yep, they are white face gauges. So, I would assume the needle was removed during that installation and installed incorrectly. That's my guess anyway.

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[Blkkbgt]

Yep, they are white face gauges. So, I would assume the needle was removed during that installation and installed incorrectly. That's my guess anyway.

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Most likely this!

I would pull the needle and simply put it back on. See if the spindle turns at all when you remove it.

 

[Sn8kebitten]

Is it possible the needle on the tach was removed at some point? I had to remove mine a while back and it is still ever so slightly off.

Now that you mention it, the middle of the 3 owners that had it after I sold it did install LED bulbs in the the cluster, so maybe he removed it? Definitely something to look into though.

Yep, they are white face gauges. So, I would assume the needle was removed during that installation and installed incorrectly. That's my guess anyway.

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As far as I know, all Cobras had white face gauges OEM, I don’t think this one has ever been changed, just the bulbs in the back. But it would be great if that turns out to be the problem