Where is the neg battery terminal grounded ?

Looks like my negative cable is loose down at the bottom. I ran my hand along the cable as far as I could, but It’s a gooey mess.

does anybody have a pic or can describe where the negative terminal line is bolted down ?

 

Just curious here as to what you mean about your issue. You think it's "loose down at the bottom" but you can't see where the bottom is? What exactly do you have going on with your truck?

 

Yesterday I went to turn the key, and nothing. Popped the hood & the connector on the negative terminal was loose grabbed a wrench tightened the clamp & didn’t look back.

this morning, the same thing….except now the clamp was tight, cleaned the terminal & clamp, no visible corrosion, moved the negative wire a bit (with the door open), and suddenly the key-in-the-ignition bell started dinging, moved the wire again & the dinging stopped, moved again ……

whether is a loose bottom ground or hidden corrosion seems the cable needs to be tightened or replaced.

oh, and I have the 4.7 (assume wring might be different for the 6)

 

It's grounded in several places, but the main engine grounds are at the rear of the cylinders heads, one on each side, in the back near where it mates to the transmission.

Picts here https://www.tundras.com/threads/ground-wire-replacement.37473/

 

I'd say pull both terminals and clean really well before diving deeper. I assume that the big ground cable off the battery has to go somewhere before anything is distributed but I'm not for sure where.

 

The Positive cable just runs to the starter, and the fuse box, but the ground splits like a tree trunk in the harness and goes to a bunch of places.

 

If the clamp was indeed tight, you should not have been able to easily move it even a bit.
Mind taking a picture of your battery hookups so we can have a closer look.

 

This is taken from a 2002 AC truck's exploded. Figure it may help put pics to words. This is best I can trace it from the pic, cable and how it splits is in green.

 

And honestly, I think it may extend farther, but the lines in the diagram made it hard to tell. Final termination may be as follows?

 

It does. If you look at it on the truck, it splits down at the bottom with two main trunk lines, one on each side of the engine, and one that runs up into the firewall and splits out to a bunch of places after that. Your diagram actually shows all the ground wires, but only part of it highlighted.

 

Looks similar enough to a 2/2.5 gen wiring. The wires from the battery (positive/negative/fuse box) go into a fat wire loom like this.
The ground wire from the battery (follow YELLOW dotted line) directly connects to what is circled in RED where it pops out of the wire loom and connects to the engine block:

 

On my 2000 4.7, the ground cable dives into the harness loom up top close to the battery, then emerges at the bottom of the loom near the middle / back of the engine. It attaches to the engine block down low and way in the back close to the trans on the drivers side. I replaced the original ground cable in a Subway parking lot in Yukon, OK. Well, more like bypassed it, the original is still in the loom, I ziptied the new one to the outside of the loom as the original could not be removed easily. And it’s longer than the numbnuts behind the parts counter says it is. Like 5-6’ long.