I would only run 2 grounds from your batteries. One to the frame one to the body. I was bored waiting for the woman to get home tonight and decided to do some voltage drops on different systems and different grounding points.

first:
I took my optima out and placed it on my tailgate, I cleaned a spot on my frame rail and hooked up a ground wire. I ran a positive wire to my starter positive and my fuse positive (0 gauge) I disconnected my efi fuse and cranked the vehicle. V-drop positive cable .9v, v-drop ground through frame .4v. This would indicate frame is more conductive.
second:
I did the same thing with the positive cable anly this time I ran a 0 gauge cable for the ground all the way back to the starter, I cleaned the lower bolt and mounted the cable there. I cranked the engine over and had the same .9v drop across the positive. This time the negative drop was also .9v, indicating a higher resistance value.

The ampmeter I used was a vat 40 (old school) and the starter draw cranking was 150 amps. I though this was too low, so I got the winch out but the load moving up the driveway was only 140 amps. I didn't have a extra set of feet for brakes or I would have tried it with a real load.

As for current flow through the frame... 400amps is not really going to cause any radio noise because the current is spread throughout the framerails/body (path of least electron resistance, think of it,is it easier to run in a small tube with 50 people or over a wide flat field?)

when I had my battery in the rear I used 3 grounds off of the battery, one to the cab, one to the frame, and one to the winch(warn requires for warranty) though my winch also goes to ground/frame.

so what am I saying? I'd just ground everything as much as possible.


Oh yea, my current grounds:
Frame to engine 2
frame to body /bed 4
engine to body 3
battery to frame body and winch
you can't have too many but one is not enough, long cables are not really needed.

Brian