Silverado 1500/Wire Routing

I will be picking up my new Silverado 1500 on Monday. I have to route some antenna wire (XMRadio and GPS receiver antennas) out the back of the cab somehow. What is the lowest profile way to get these antennas out and on top of the cab? The truck will be a lease so I can't drill any holes. Is there an access hole somewhere in the back of the cab? I don't have the back sliding window option.
Thanks, Dan H

Try routing it through the third brake light. You can very slightly notch the gasket to route the cable and fill it with silicon (or a new gasket) when you are done.
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Greetings,
I've recently installed XM in my Silverado (a Delphi SkyFi2) and I find that the antenna works just fine when placed on the dash. You can run the antenna wire inside the seams of the dash along the windshield then down along the side into the fuse box on the driver's side where you can coil up any spare wire and secure it with a zip tie. From there it's easy to run it under the dash and into the back of your unit's receiver or dock.
I also used the direct FM adapter that plugs in between the stereo's antenna connectors to improve the sound of my XM unit and eliminate interference from local FM radio stations. The antenna cable has a connector link just behind the glove box and is very easy to get to to install the adapter.
As for a GPS unit, I occasionally use a handheld unit inside my truck, and as long as it sits on the dash it receives very well so I imagine that your GPS receiver antenna can go on the dash as well.
If all of this doesn't appeal to you, then on my truck (which is a crew cab) there are air exhaust vents on the back of the cab wall near the bottom on both sides that you can get a wire through.
Cheers - Jonathan
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I also had to route my GPS and XM antenna to the outside. Outside is the BEST. Sure some people route on the inside, and have it under the window, but you still get dropout, unless you live in a City with Ground Repeaters everywhere in which case the Antenna inside works fine until you leave the area.
It's actually pretty simple to remove the 3rd brake light and run the wires though there. In fact there are holes behind that light already large enough to pass the wire plugs though, that go right inside the cab above the headliner. What I did is get about a 3 foot piece of welding rod and taped on good the wire ends to it, and then I carefully pushed that stiff welding rod into the cab and to the passenger side, then you can carefully remove the hand grips on the headliner by using a small screwdriver to popup the 2 plugs on each end and they come right off, you can then carefully reach up above the headliner and grab the welding rod and pull the wires though. This way your pulling the whole headliner down, then you can run both wires down the passenger side above the headliner and down the windshield side cover which Pops off, Pull carefully on Top and it'll come off. Run the wires down, then behind the glove box and then to where ever you need them at.
It's really easy. It was simpler then I thought it was going to be. In fact I'm on my 3rd XM antenna because I upgrade to the newest smallest one I can get. Wish I could find a bit smaller GPS antenna. Depending on the wire size you may not have to do anything when putting on the 3rd brake light, it may seal it's self, it should is it was just the XM antenna because the wire is SMALL. The GPS wire though is a little larger. I did have a minor leak with that one, but I just tighten the screws a bit more after a few weeks and it sealed right up. I thought about using silicon, but if I have to change the light, that will be a hassle, and 3rd brake lights do like to burn out a lot!
I also ran the antenna wires on the roof to where they were the same width as the light and not just right next to each other. Works great. It takes a lot to loose a signal. and if I had to turn the truck in later because of lease I can have that antenna removed in a couple minutes. (That fast!) I don't know what kind of XM Radio your going to use, but I have a Skyfi 2, and I use a Pro-Fit custom mount. Looks good and can be easily enough Removed. Also using a PAC Direct Connect Interface to get a direct connection into the Radio from the Skyfi, because Wireless FM Modulation SUCKS! I did have wired FM Modulation for a while but only because there was no direct connection at the time. I'm also setup so the Skyfi 2 Turns on and off with the trucks Radio though the R.A.P. system. Which is nice. I have 1 Subscription with the Skyfi 2 and can tune in not only in my truck,(The Radio display SUCKS for Satellite radio and so do the controls), but I pop it into my Boombox and work and at one of my 2 home cradles. I like it. AS for the GPS, I'm using a Garmin 2610.
I have a 03 Silverado Extra Cab.
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