Ford Repair: speedometer on RV E-350, vehicle speed sensor, speedo cable

Question
The speedometer on my RV (Ford E-350, 1995) works fine up to 50mph. after that it bounces as in a cable that needs lube. Is it possible to lube the cable?

Answer
Hello Paul, A speedo cable can be lubed but I think the cluster is electronic. That means it does not use a cable it uses an sensor for electricial reference. The vehicle speed sensor could be acting up or it is in the instrument cluster itself. Hope this helps Thanks Tony