I looked around and didn't find a real thread on how to wire through the firewall on the drivers side. I want to run a wire from my cab through the firewall under the truck and into the bed. So. How do you do that?

 

On my Ram there is large-ish almost oval looking piece of rubber on the left side of the brake booster, that's the access to wire through the firewall.

Simply feed the wire through there (usually something stiff like a metal coat hanger and the lines taped to it works) and simply run the wire out of the way of moving parts underneath the truck.

 

I ran mine out thru a Grommet by the Door Hinge. Mine had 2 Unused ones.
You can see the bundle of colors.

 

Where did the wires go after running through the door Grommet?

 

I ran them into the Fender, you can go Either up, or Down. Its alot easier to remove the Inner fender if you go down tho.
I just tucked them behind the foam thats between the fender and cab

 

Do I have to remove the fender?

 

That's how I ran my wires. Both for my sub and my off road lights.

 

No just the Inner Plastic part, Its held in by Push Clips. (You might need to replaced them, I had to break my OEM ones to get them off) They arnt expensive, Also the Front Splash Guard needs to be removed, Its also held on by Push Clips.

 

Most auto supply shops should have rubber grommets of various sizes. Select one that would fit a hole large enough for all your wires and then using a hole saw (the white bi-metalic blades work best for me) cut a hole in the most convenient place, touch up the bare metal with some sealant and then pop the grommet through the hole and run your wire through. I'd recommend making the cut from the inside to the outside, this way, if the saw skips, you won't damage the outside paint (make a small pilot hole first). Before you cut, make sure there's nothing on the other side that you can damage.

 

If you skip a hole saw, your doing it wrong. haha
Everyone Ive used or seen have pilot drill bits on them, to prevent it.
Like said above, Make SURE to touch up the bare metal with primer, or some kind of sealant to prevent rust.