[davidlee]

ox ford guy
I had the some problem on a non-cobra car{speedo worked with a drill hooked to the plastc gear but not when hooked up to the tranny} Come to find out the speedo cable {the inner one} was just enough too short when it was hooked up to the tranny the bend in the cable made the inner cable not quite long enough to mate into the plastic speedo gear. I bet I took the ---thing apart ten times and could not figure out the problem. Finally I figured it out. In my case the part that goes into the tailshaft of the tranny had two cable adaptors {a short piece of cable with a male and a female end on each one} so all I did was to put a spacer in between the adaptors to lengthen the cable. Problem solved. I don't remember if my Cobra had any adaptors but you accomplish the same thing by shortening the cable housing just a tad.
Hope this helps

David