The cable housing can still be bad. Mine was jumping even after I lubed it. I replaced the cable and it got a lot better. Still jumped some.
When I had it out of the car I hooked a dremel tool cable up to it and put a drill on the other end. It ran the speedo nicely and I picked the best of the two speedos I tested.
Same with my 66. I had lubed and cleaned the speedo and cable a couple times. I went to NAPA and got a new cable assm. and it took care of the problems. (jumping, jittery needle, noise)