The speedometer on my 1965 convertible stopped working. First it was sluggish, and then stopped working. I had someone look at it and when the cable is not connected to the tranny and it is turned, the speedometer works. They changed the plastic gear, and now it still doesn't work, although every once in a while it jumps a little. I noticed on some of the parts sites that there are actually 5 different gears for this years model, ranging from 16 t0 20 teeth on them. I do not have the original gear, and can't get it,and was wondering if anyone knows which one I need. The car was built in April 1965. If the gear isn't the problem, any other ideas. Thanks for any help.

Try replacing the cable itself. It is probably worn on the end that goes into the plastic gear.

I agree with Jim, Could be your cable. The number of teeth depends on your rear end ratio. The tag on your door should have that info if the rear is original.