Triumph Repair: transmission mounts, grounding cable, diameter

Question
I'm working on a 1978 1500 spitfire.The transmission and engine were out of the car when i got it.There is a cable on the bottom of the mount plate were the transmission mounts go. This cable is about 5/16 in diameter and has threads on both ends. What does it hook to? It looks like it should go towards the engine.The back hooks to a little box looking plate.How does it adjust and what does it do?

Answer
To be honest, I've never figured it out.  some have that cable, some don't.  most cars I've seen don't.  It could be a grounding cable for the transmission.  I've only ever seen it between the rear plate of the engine and the transmission mounts.

Sorry I can't be of more help.