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driveshaft vibration cause false knock

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Old Feb 6, 2006 | 03:56 PM
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Default driveshaft vibration cause false knock

can a bad driveshaft vibration cause false knock?
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Old Feb 6, 2006 | 09:45 PM
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Theoretically it shouldn't, it would be in the wrong frequency range. BUT anything is possible.
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Old Feb 7, 2006 | 01:16 AM
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The only way to find out is swap it with another!

I guess it wouldn't but anytime a vibration is produced just the vibration will cause 2st, 3ed, or ever 4th harmonics of lesser magnitudes. Those could be in that range.

I don't know dude. With my tize size and rear end I calculated that my driveshaft would be rotating about 56.77 times a second. 80 MPH, tire diameter of 27 inches, standard rear end for M6. So any oscillation would be about 60 hertz right? Well multiply that by 2 3 4 ect to find the harmonics. Nothing about 6,400 hertz which is what the knock sensor is looking for.

Wheel Diameter is 27 inches. Circumerence is 2*pi*r so 84.82 inches

If going 80 MPH that is ( 5068800 inches / 1 hour ) or (1408 inches / 1 sec)

That is (16.6 rotations / 1 second)

The rear end is 3.42... so 16.6*3.42 is (56.77 rotations / 1 second)

One hertz is one oscillation per second. Therefore (56.77 r / 1 sec) --> ~60 Hertz It would take 10 harmonic series to even hit in the needed frequency. It would be way to faint. That is my 2 cents!!!!
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Old Feb 7, 2006 | 01:17 AM
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Going to have a beer now. :-)
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