I want to run some wires from the cab to the engine bay. Where is the best location to drill a hole in the firewall. It seems the firewall in the cab side is covered in some insulation type stuff. I dont want to drill a hole and take out some wires behind the insulation layer.

Also, can wires be run throught the air vents in the rear of the cab? Like a CB antenna wire.

Yes you can run stuff through the vents or I did anyway. I drilled a hole kinda by the gas pedal that is supposed to be used for the snow plow prep.

Edit: others have found ways to get it into the cab without drilling though.....

On the driver side firewall is a rubber grommet which you can pop out to run the wires through and the put it back in place when your done...no drilling required.

are they on the 05's?

Ahh, that I'm not sure...but I doubt GM has changed the firewall. The plug is rubber and can be a bit of a struggle to get put back in place but beat drilling. I used it for all of my in cab power leads.

Ahh, that I'm not sure...but I doubt GM has changed the firewall. The plug is rubber and can be a bit of a struggle to get put back in place but beat drilling. I used it for all of my in cab power leads.


Are you talking about the main one that has all the wires running through it? Or is it an unused one?

On the 05's there is a place on the drivers side that is round with no insulation. Nice flat space to drill with nothing behind it. I got several grommets from the junk yard that worked well.

follow the yellow wire in this link.
http://www.dieselplace.com/forum/attachment.php?attachmentid=2308