heres a link to the review i did on the garmin nuvi 660 with install pics etc.
gps install - Dodge Diesel - Diesel Truck Resource Forums
Not trying to hijack this thread, just showing another person's solution that may pan out to be pretty decent also - Time will tell. .
Really liked the above review & Installation. It motivated me to get out and put mine in a more permanent location (that did not compromise any existing features on the dash).
Originally, I liked the higher, heads-up approach for convenience, but then realized it doesnt do much good if it gets stolen. With that in mind, a low key approach was taken instead. It is easily removable with a pull of the bottom tab (it comes out easily from its cradle). After trying all kinds of locations, there was almost always a reason why it didnt work there, like covering up a dash control, too easily hit by the stick shift, scratched by keys, hit by my hand if it was too close to the steering wheel, etc. I soon found out, mounting one of these new models can be kind of a bear if you want it out of plain view.
Also, did not want to lose the original Garmin V due to its excellent off-road features the new Nuvi 680 does not have.
The plan ended up being this: Use the Garmin Nuvi 680 for street navigation, hands free phone via its excellent bluetooth capability, traffic updates, and since I sit in traffic a lot here in the city, I like the audio book feature and it can even transmit its audio to the truck's FM receiver so you can listen to it via the stereo, which means it becomes an MP3 player as well, and it even works for the phone so you hear your caller in surround sound (well almost). There are a lot of nice features on these new units, but this one doesn't have the off-road tracking ability, so. .
The existing Garmin V became the dedicated off-road nav unit and the compass and trip stats machine (speed, time, miles, elevation, etc). Ended up removing all of the street maps and totally loaded it up with... TOPOS! Lots of topo maps, great for off-roading, exploring, geocaching, finding your hidden lakes up in the sierras, etc.
They are both hard wired in so they always have power independent of the ignition switch. The existing G-V had an external antenna connected that was mounted way up forward on the dash for good reception, but have found the new unit has such a good receiver, it has no problem getting good enough signals to do its job fine without an external antenna. Of course it has a plug for one if it becomes necessary.
See full-size pics here while my DHCP IP lasts...
http://75.140.70.182:13200/Truck Pics/GPS_Install/
Also will try to upload full-size pics to the Photo Gallery if anyone is interested in some additional features.
Note: I purposely edited out my coordinates off the pics that's one reason why they look strange.
The mount was done by using the supplied mounting disk, removed the factory adhesive tape, ruffed up and prepped the surfaces with denatured alcohol, used grey RTV silicone in the center of the disk, used clear epoxy around the silicone almost out to the edges, but left a slight margin around the edge to finish off with a clean appearance, dashboard matching grey silicone out to the edge for a little more professional look, but mostly for a sort of rubber mounting with some epoxy for strength. Seems pretty solid! Then used the standard suction-cup/swivel mount to make the attachment. Tie-wrapped the wires neatly up under the dash and as much as possible along the oem radio feedline to try to induce the output signal to the stereo.
The mounting disk was mounted right on the front flat surface of, yes. . the ash tray. . Hey, the whole unit swivels down with the ash tray and just clears the 4x4 lever by about 3/16 inch and everything retains full functionality.
The pics show the transmission in first gear to show there is adequate clearance. Also, the keys don't even come close to the Nuvi's screen, so that is not a problem.
In the dash illumination pic, the Garmin-V's brightness is set a little too high, but can be turned down so it doesn't overpower the intensity of the other instruments. .
See for yourself. .
Happy New Year!