Since installing a 2002 4.6 and 4R70W transmission in my 61 Galaxie, I never had a functioning speedometer. The 4R70W transmission is an electronic transmission and sends an electronic signal from the transmission via a Vehicle Speed Sensor(VSS) to an electronic speedometer. The VSS is located in the same position on the tail shaft housing that a speedometer cable would be. As you are aware, the speedometer on a 61 is a mechanical gauge. I thought the only option for a speedometer would be to buy an available converter which takes the electronic signal from the VSS, converts that signal to voltage and then supplies an electric motor which in turn spins a mechanical cable. These "Black Boxes" are pricey at around $350.00.
After doing some research I figured out a simple and much cheaper way to get my mechanical speedometer to work from the electronic transmission.
I was surprised to learn that the VSS sensor on my 2002 has a mechanical drive option and will accept a speedometer cable. Many Ford vehicles between 1983 and up to 1997 used a VSS sensor in combination with a speedometer cable. 
So here is how it all went down:

Below are two VSS sensors. However, the right sensor has the plug removed. Pop that plug out(you will damage it doing so) and it reveals and inlet for a speedometer cable. Make sure the O ring in the VSS remains.
I harvested a speedometer cable from a 1987 Mustang. Note that the cable has a snap on end which goes onto the speedometer head, versus the 61 cable which uses a thread on end.
I removed the plastic clip from the Mustang cable cut the metal housing off and ground down the remaining flange to fit into the harvested speedometer cable nut. I got that nut from a 1970 Ford Van. I cut a slot into the nut with a hacksaw, and cleaned the threads to accept the cable. Finally, I had to cut the exposed end of the drive cable before inserting into the speedometer head so that it was the same length as the Galaxie's. Before:
After:
The other end of the Mustang cable pushes into the VSS sensor and is held in place by a spring clip.
Next spring when I start driving the car, I will have to experiment with plastic gears located on the other end of the VSS sensor to calibrate the correct speed. Total cost was the cable at $10.00 and a few hours of time. 

Last edited by dan_6776 (November 22, 2016 9:10 pm)