How are you supposed to remove the speedometer cable
I could be wrong. At some point I noticed in the shop manual the sequence was specific about removing the pinion housing before disconnecting the cable. Of course I can't find the page right now. :(
I don't have a '76 FSM. This was probably in '67 or '68 which I have print copies and use alot.
My '67 225/904 had the original cable and you can see how tight and almost continuous the threaded nut is to the crimped part of ferule. Sorry I can't find a pic with it removed, but it never spun free.
Not the best photo, but the nut on replacement cable overlaps the crimped housing.
(The frayed cloth end is a heat insulation sleeve)