Not a hard job...

Both primary grounds go to studs on the front lower side of the engine.
On the passenger side one cable goes to the starter relay which is the charge line from the alternator.
One goes from the starter relay to the starter to the solenoid.
The heavy cable at least 2/0 goes from the passenger battery to the starter by going down then back past the engine mound. You will have a cable clamp for the back pass through which is the same stud for the passenger primary battery ground.
The cross over should be at least 1/0 form driver to passenger battery recommend 2/0
You should also have secondary grounds from both batteries to the fenders.
I made custom cables and had everything changed out in about four hours. But also have a strong background in doing these kind of jobs.

Make sure you get real copper welding cables not copper clad welding cables.

If you order quality cables with all ends made up you should be able to do the job in a few hours with basic tools.

EDIT.....
Strongly recommend military style battery clamps for everything. You will be able to change them out without changing cables like the stock setup when they get stretched or corroded.
Battery washers on cleaned batteries with proper battery grease will go a long way on making the new cables last.

 

Not a hard job...

Both primary grounds go to studs on the front lower side of the engine.
On the passenger side one cable goes to the starter relay which is the charge line from the alternator.
One goes from the starter relay to the starter to the solenoid.
The heavy cable at least 2/0 goes from the passenger battery to the starter by going down then back past the engine mound. You will have a cable clamp for the back pass through which is the same stud for the passenger primary battery ground.
The cross over should be at least 1/0 form driver to passenger battery recommend 2/0
You should also have secondary grounds from both batteries to the fenders.
I made custom cables and had everything changed out in about four hours. But also have a strong background in doing these kind of jobs.

Make sure you get real copper welding cables not copper clad welding cables.

If you order quality cables with all ends made up you should be able to do the job in a few hours with basic tools.

EDIT.....
Strongly recommend military style battery clamps for everything. You will be able to change them out without changing cables like the stock setup when they get stretched or corroded.
Battery washers on cleaned batteries with proper battery grease will go a long way on making the new cables last.

Thank you, encouraging!! I'm not making my own cables, the suppliers name is Custom Battery Cables. Appear very heavy duty and also fairly expensive. Again, thanks for your response.

 

Custom Battery Cables are very good quality. I'm in the middle of putting a set going on a customer truck currently.

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Missed adding engine block to frame on both sides as well. No need to be over 1/0 but use what you have, 1 AWG is more than enough and likely overkill at that.

 

When I did mine I put an additional ground from the drivers side frame rail to one of the drivers side bell housing bolts. This way, the transmission is sure to be properly grounded, which I’ve heard can be an issue. I also ran an additional ground to the drivers side negative to one of the alternator mounting bolts


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The concept of grounding the transmission had to be one of the most nonsensical ideas out there. It's by design isolated from everything else with the exception to the engine block. If you attach a negative cable to it, it becomes a parallel circuit.

 

You're not being picky. I end up missusing that term to get people to think of the body tub as a unified source, and it spills over in posts where I'm typing away. The frame acts as a non-enclosed busbar, the electron pathway to the lights, etc.

 

I know a lot of people on the forum hate this guy, but the transmission guys seem like they know what they’re talking about & have lots of real word experience with this possible issue


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It's a good excuse for trans guys when they jam the pump.

Where's the pathway, or do we need string theory to find it.

 

I can't even remember when my Fluke looked like that!

 

I can't even remember when my Fluke looked like that!

It's my precious, kept in its case. The older fluke gets the grunt work.

 

Interesting. So if one wanted to add a ground to the transmission, the right way would be to run it to the negative battery terminal rather than the frame? I’m not sure I understand


When the engine is attached to the trans, the block grounds everything to the negative battery posts. The small ground strap on the back of the block connects the block to the cab, and the small ground straps under the doors ground the cab to the frame. So what’s the harm in adding an additional ground from the trans to the frame?

Not trying to argue with you, genuinely trying to learn


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The connection on a bell housing bolt should be a pathway directly to the engine block, with some degradation over time. That should not be going through the front pump unless the connection degrades. But it becomes another parallel circuit, now flowing some current. How much current depends on the main block to battery to frame connection at the passenger lower front of the engine block. When that connection degrades, current flow increases through the other pathways. When it gets poor enough, you usually find the 12ga braided cable under the footwell burn up, occurring when the starter is engaged. The starter is a hungry beast for a short time and will alter the flow throughout the braided cables. Early Powerstrokes had a recall to improve the primary connection, changing the stud and the tension. It also warned about the block to firewall 12ga braided cable being burned, but it never mentioned the footwell cable, which is the one that has a higher occurrence of burnout.

I'm not a fan of the OE layout and have made several videos about the negative pathways. I've also had videos of improving battery to battery and the need to add another 8ga negative cable from the driver's battery to the driver's side inner fender. The battery to battery was showing a method to help, although it's still not ideal. It was not to have people pay a ridiculous amount of money for a popular set. I still have two more videos to finish the group; why the 8ga negative is needed and a better design main cable set, well, maybe two different ways.

Back to the question, adding a cable to the trans, which Ford says not to do, adds a potential pathway that could do damage if the starter current goes through the trans. So it's better to make sure the primary connection is good every few years.

The existing cables as they exist are very dynamic, altering flow direction between key-on, starter engagement, and running. This work was done before the ideal of a trans cable was brought up or I would have added that to the tests. I still might at some point, but I've got enough on my plate.

 

Appreciate all the responses, ordered my cable Saturday.

 

I have to say changing cables and connectors made my 08 6.4 run much better.I started job but ended up letting local ford shop finish ,very satisfied price and quality of work done.

 

I've had min rigged for a little while since the main + terminal broke. So I just bought a hydraulic crimper and some anchor crimp terminals and the diehard steel battery terminal to bolt them to.

 

Received my cables last week, very impressive. Plan to install Saturday, getting mentally prepared now!

 

Update, found out it's not that fun for a 67 year old man to lay on his back under a truck!!
Got the starter off, top bolt was a killer for two reasons 1. which I mentioned above and 2. location of the bolt and being covered in a half inch of dirt, oil etc.

Decided start on the driver's, I took the battery box and intercooler pipe off to easily see routing of the ground cable which is not that bad. Location of bolt on engine block not bad but had two issues 1. which I mentioned above and 2. I believe it's an 18 mm but I could not get a good grip and was afraid I'd round off the corners, found this out after doing my best to clean off a half inch of dirt, oil etc.
Get this, the small ground from battery to body was cut.

Passenger side cables and locations not too bad except for two things, 1. which I mentioned above and 2. the ground cable to the block has a small ground ground wired in near the eyelet. What could that be? my plan was to cut the cable right above the small wire and and use the eyelet for grounding i.e. ground from the block eyelet and small wire ground eyelet.

Starter installation I figured would not be too hard except for the one thing mentioned above!

Long story short, I have a well recommended mobile mechanic coming to give an estimate for finishing the job.

Cheers