Dan writes - "Shock-Proof your Garmin GPS to prevent unintended power-downs. I look at a couple different ways to make the fix, and actually do one of them. This project requires soldering a couple of fairly tricky connections inside the otherwise working GPS, so use caution." - Link.
http://blog.makezine.com/archive/2006/05/how_to_shockproof_your_ga.html