[shorod]

Welcome to the forum!

If you have a cable that runs the speedo, then it goes all the way to the tranny and has a mechanical connection there as well. The mechanical interface to the tranny will be through the vehicle speed sensor though, which is effectively a DC generator which is gear-driven off of the transmission to provide a varying DC voltage to the PCM and cruise control unit.

The problem with the bouncing speedo needle may be in the speedo head rather than in the cable. Lubing the cable may have allowed enough temporary lubrication to get into the speedo and temporarily reduce the bouncing. Or, maybe you didn't get enough lube on the cable and the new cable has absorbed all the grease already.

-Rod