Advice please

Go through the firewall

 

i always just ran it out the door. do it where you have the rubber seal. i 've never damaged a coax that way

 

Works good if you're driving a car, not so much on big trucks. Once you get through the firewall, then you have the dash to contend with. The OP said that he can not disassemble the dash, or take things apart.

Also might not be able to secure the coax from the mirror bracket down to where you would go under the hood, so it would be left flapping in the breeze, something DOT may not appreciate...

 

I've seen them break after wacking a branch.

 

sooner or later tree branches with take out anything

 

For those that don't wish to go through the door, the firewall is usually a decent alternative. The coax can be secured in several places and there is also many options of going through the firewall low enough so you aren't fighting with the dash. There's always exceptions but generally where there's a will there's a way.

 

I have never tried these but....I have heard that using an old speedometer cable can be used to thread through the existing holes in the truck to then pull the coax through.
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Option 2, by running the coax through a small diameter piece of tubing will keep the door from crushing/damaging the coax when running the coax through the door weather stripping.