Triumph Repair/speeddometer cable
1976 trimuph spitfire: where does the cable connect both ends upper and lower
There were two different systems used. The earlier version had a EGR service indicator unit and two cables. One from the rear of the transmission to the service indicator and a second cable from the service indicator to the rear of the speedometer. The other system had a long cable from the rear of the transmission to the back of the speedometer.
It was difficult to remove the rear end at the transmission so it was easier to remove the transmission tunnel to gain access to the rear cable connection which was either a bolt through a fork that held the cable housing to the transmission or a nut on the cable to a 90 degree drive attached to the transmission rear housing.
To gain access to the back of the speedometer you can best remove the tach and reach through that hole. It may also be necessary to remove the center dash panel depending on which version you have.