Mazda Repair: 90 miata, shaft assembly, odometer

Question
I hear a noise inside the care when I am driving. My odometer starts shaking and that is when i hear the noise. Does that mean I have to replace the odometer cord. Or what could it be

Answer
As the speedometer cables helical shaft begins to fail it makes a "warbling" noise (best description) which appears to come from the center dash/cowl.  In unison the needle tends to  hop or flutter in response usually below 40 MPH.  The most common fix is to replace the cable.  It runs $86.30 from Mazda and takes some talent and flexibility to replace, usually 1.2 billed hours.  

Here we make a service fitting for the cable which allows you to inject low viscosity grease into the helical shaft assembly thereby extending its service life.  The tool sells for $29.95, NAO1-513-SC.  Depending on how much wear has occurred to the helical shaft lubricating seems to resolve the issue also.

service@miatashop.com