Don't know if my speedo dances at 60mph or not, since I haven't been over about 45 mph yet. If you can pull the cable itself out of the sheath/outer cable, you could try lubing the inner cable with something like "Sil-Glyde". Its kind of a clear grease like substance you could squeeze some out of the tube and coat the inner section with your finger and then slide it back in. Also, There are often speedo rtepair shops in a city. Tacoma, Wa has one, and Seattle used to.
JOn