I am currently taking out my cluster gauge so I can replace the bulbs. I have everything disconnected on the back. I can't really see. But I can't seem to disconnect the thick wire going into the back of the speedo. I can't see if there is a bolt on it. So just wanted to see if anyone knows how to disconnect it?

 

some years have a clip like a door lock.
More commonly it unscrews. Should be hand tight, but after a few years you may need to get channel locks on it and turn. If needed you can unhook it from the tranny and then pull the cluster out farther. This will let you see what it needs.

 

It is a clip. Kind of a finagle to get it off. Pulling it off the tranny may of may not work. Depends on how well the cable is sealed to the firewall.