I finally figured out why my truck acts funny and starts on the dime sometimes and most of the time acts like the battery is completely dead. I've decided to replace the cables for the battery starting from the bottom. Where does the negative battery cable trace down to from the battery? do I need to take off the passenger wheel to access it? I work at home with no lift or ramps.

 

A lot of times, it will be a short cable bolted to the firewall. The engine is grounded to the frame, and another cable to the firewall. The starter might be grounded to the frame, etc.
Presumably this economy with copper wire shaved off pennies per vehicle. Hm.
On the old stuff it's common to just run a heavy cable direct to the starter. Clean, tight grounds and connections keep the magic smoke inside the boxes and electrons flowing where they need to go.

 

The 2000 Navigator manual shows a grounding harness, with a ground going to the starter itself, and one up above near the engine and the firewall. It's all made together with the + cables and is taken out as an assembly.