Funny bouncing speedometer needle

So my speedometer cable bounces around all over the place now - even at highway speeds it goes from 50 to 85 mph and back and forth and back and forth. bouncing all around. it used to only do this around 10mph. Is there a fix for this? It's pretty amusing to watch. Good thing i have the scanmaster for the real speed (that number stays steady)
Yep, replace or lube the speedo cables (before and after the cruise control)

The cable is binding and letting go causing the bounce.
Mine has been doing that since I bought the car (2 years ago in Dec.). At 30mph and above, it's pretty steady though. What can you use to lube the cables?