How do I lube a speedometer cable

Hey guys,

My speedometer cable on my 74 duster bounces really bad from 10 to 20 and then like drops after 80 to 120 so I was wondering first off does it need to be lube and how do I do that

Thanks
You could pull the dash, then take the cable off the speedo and shoot some WD 40 down there, but it would be easier to just replace it 9and not have to pull the dash)