1979 TA Speedo not working - help please!

[smokey]

So, my speedo suddenly stopped working. I have disconnected the cable at the end which goes into the engine bay and if I twist the end of the metal inner cable the speedo needle moves, so I know the cable is fine... Right?

I then marked the hole that it goes into with a tiny bit of white tipex and got my missus to slowly drive the car forward slowly while I walked alongside to checked if it spun at all (this is the part that should spin which connects to the cable, making the cable spin, sorry I don't know it's correct name).
It didn't spin... Any ideas???

[Mikey V8]

Have you checked the back of the speedo?

[thirdgen]

kevs speedo has not moved in years

[SUPERCHARGEDGTA]

did you disconnect the cable at the cruise control unit or the gearbox?
there is one cable between gearbox and cruise control, then another one from cruise control to speedo
if you only did the top one then it could be the lower cable gone or the speedo drive in the gearbox

[smokey]

Update: I disconnected the speedo cable from the cruise control unit and twisted the cable with my fingers while someone check to see if the speedo needle moved... It did!

Then while driving the car very slowly someone walked alongside and looked at the cruise control unit to see if the part that should make the cable spin (gear) was spinning... Which it wasn't.

Then I disconnected the other cable that goes to the gearbox at the cruise control unit. I then drove the car slowly again to see if the inside of the cable was spinning... It was!

So it must be something in the cruise control box right? Any suggestions?

[SUPERCHARGEDGTA]

get a new cruise control unit
is rev counter working ok?