Roger,
If you know the cable is the source of the noise, then you should be able to disconnect the cable at the block, hold it high above the bay, and drip some ATF down the shaft. I think you can even remove the core cable inside the housing and thread it back in. You just need to have it get back to the tach and have it slot back in. Joe A did this with mine last spring, but it did not fix my howl.
With mine, and many others, the tach howls from within, especially when the weather drops below 50 degrees. In this case, it makes the most sense to have a tach and speedo shop disassemble it, clean and lube it and replace any bushings inside. (just paid $75 plus freight both ways).
The knuckles stop bleeding in a few hours, and the resulting scars are kind of a badge of honor.
Good luck.
Mike Mizesko
Columbus, OH