speedometer cable (bouncy)

I recently replaced speedo cable in my 66 as it was leaking C4 transmission oil. Everything went fine - no more oil on floor - but now my speedometer bounces at slow speeds - below 20 mph it will bounce from 0 to 20. Once I reach 20 and up it smooths right out. I'm wondering if I introduced a problem or if thats the way these speedos work. I would not have even looked at the speedo at such slow speeds if I had not just replaced the cable. I lubed it with speedo grease per the instructions. Anybody else ever see a bouncy speedo at slow speeds?

Ronstang: I did the cable thing you mentioned - no change - I now have the speedo on my work bench and am trying to figure out how/what to lube. Does the cable insert come out - is that what you lube? It dosn't look like something that's easy to disassemble. mfp4073: I reused the transmission gear - it looked fine.

New info on my bouncing speedo: (1) I bought the cheap one for 20 bucks and it is a one size fits all - it's about 2 foot longer than my original. (2) Although I threw away the original I seem to remember it was not only shorter in length but built out of stouter material. (3) The Ford built replacement was about 60 - 70 dollars - am I on to something or do I need to keep trying to make this new #@&#! cheap one work?

I love it when a plan comes together. After spending way more time on this than I should have had to - NO MORE BOUNCING SPEEDOMETER CABLE! For all those who followed me on my journey the fix was simple - I bought another cable from NAPA. As soon as I examined the new cable I new I had it - when I would hold one end of the cable and twist, the other end immediately twisted. The other POS that I got from BEL-KIRK MUSTANG I could hold one end and twist - nothing happened on the other end - kinda like rotating a spring - I could feel the tension but it wouldn't turn in my hand until I had gone thru 1 complete rotation on the other end. That's why the speedo was bouncing at the slow speeds - at the higher speeds the torsional effect would be dampened out resulting in little or no bounce. The above post contains an error - there is only about 4" difference in length between the 2 units. Also, only had to pay $25.00 for the NAPA unit. I had called the local Ford dealer and they no longer carry them - they recommended I try NAPA or Westbay (another parts place). I typing fast here as my computer monitor is starting to shrink - LOL it's always something. Again, thanks to all who replied - they were good tips.

TTT - I now have a new monitor - wish they went for only $25.00