Open it up; it's just a QD; quick Disconnect.OOps,You already said that,lol.
OK so follow it along to the other end. Notice that it is a thinner gauge wire than what is at the two ends. That makes it a fusible link. It protects the main wire by sacrificing itself in the event of an overload.
But, It doesn't blow like a fuse. A fuse responds to an overload instantly. Whereas a F-link can run hot for quite some time before expiring. And it can survive multiple events.
F-links are color coded. If your original wire is completely gone you will have to refer to the wiring diagram to see what color the replacement needs to be. While you can put anything in there that you care to, the only proper repair (if you value the truck) is by replacement with the correct color part.You can get plug-in links at the dealer, splice-ins at jobbers. Soldering these is NOT a reliable repair.Plug-in is best.
Of course you need to figure out what caused the failure and fix that first. Isolate the circuit to find the hi-current draws on the line and start checking them one-by-one. If no fuses down the line are blown, then you'll have to start looking at various connections. And it may even be that someone has already replaced the offending device, and just never bothered to properly repair the F-link.
BUT
The only time I have seen that large a cable with a QD on it, it was supplying multiple F-links. Like three of more.
And sometimes there's no fusible link at all following, it may just be a splitter on a high-current line like the alternator output.
I have a feeling that QD should have two cables coming out of it, both headed for the #1 splice; a fat red one and a fat black one. From that #1splice , power is routed everywhere including another pair of fat wires to the alternator. At the #1 splice,there may be as many as 10 or more wires all connected together.They call it a weld. Some of the other places those wires go to are; ignition switch, fuse-box,computer, A/C system,or to other splices.Some of those may have their own F-links.
I guess the bottom line is,you need a wiring diagram.