at 55 my speedo needle jumps and makes a terrible noise. suspect is bad cable. any thoughts?

'94 2.3L 2wd 5spd

 

The only cable I have ever had to change was on my 89 mustang.There is a clip that holds it to the undercarraige just before it goes into the fire wall. The cable cracked there and the wire that wraps around the speedo cable was exposed. Got to be rusted up on the inside if thats what has happened to yours. Mine bounced till it hit 20 mph.