What gives with my speedometer cable?

[JHZR2]

Hi,

This is on my 82 300CD. In december during a cold spell, out of the blue I got a horrible screeching sound from my speedometer cable. So bad that I had to pull off the highway and disconnect.

I got some speedometer cable lube (black liquid) and applied it to the cable per the instructions. Was great after that, not that Ive run the car much this winter. But it showed far less bounce, no noise, very smooth.

This morning I go to drive the car about 35 miles. The bounce is back, but only sometimes, like it comes and goes depending upon how severe the last pothole was. At about 30 MPH, Id start to hear a slight whirring noise, though it would go away after 50ish. Sometimes it is audible, sometimes it is not. Sometimes it is bouncing, sometimes it is not.

Does this mean that I just need a new speedometer cable? Tried fiddling around a bit with the routing, but nothing helps.

Thoughts?