Annoying Speedometer Noise at Cluster

There is a specific moly loaded speedo cable lube that you can get and it's made to not solidify in even very cold temps. A moly loaded lifter lube will work well too. Try to find that. Lithium grease is also used but will dry out with heat over a few years and need to be renewed. You need to pull the calbe core out to lube it from end to end.

The speedo cable end may not be fully seated in the back of the speedo housing, and the old lube is making things worse. I have had your exact same problem with a Dart speedo, with the jumping and misreading, and thought it was not the cable, but I finally got it relubed well and the cable end reseated correctly and that fixed it.

If the end is rounded off of the cable core, which is another possible issue, then you used to be able to get kits that can be cut to length with a crimp on new end. I've used those before and they worked fine.