To set up your rig to transmit your GPS coordinates as APRS packets, you need to make a few interconnecting cables. For maximum flexibility I made the ones shown in the photo below.
Assuming your car is fairly new and can suply 10 A to your 12 V accessory outlet (older cars often can't!), make a cable with a cigarette lighter adapter on one end and PowerPoles on the other. For times when you'll use TinyTrak3+/GPS, you need a splitter to supply power to both rig and TT3+/GPS. In addition you'll probably want some sort of extension cable to be able to put the rig where ever is most suitable. For times when you're not using APRS, the splitter and TT3+/GPS are of course removed.
When you hook it all up, it looks like this:
Then you're ready to hit the road! One final note: To switch between using your mobile rig and an HT as the APRS tx, you might also need to use an adapter to convert to the proper packet connector for the less commonly used transceiver.