[Goakley86]

So I have a 2004 Chevy crew cab Z-71 with 220,000 miles. It has recently started having a ticking sound coming from somewhere in the drive train. I can only hear it when I'm driving next to a building with the windo down "like going thru a drive thru". The sound will speed up and slow down with acceleration, and deceleration. In just looking for a place to start.

 

[Gozzie]

With 220k it's probably in the valve train. Not to worry unless your oil pressures have changed.
It could be an exhaust gasket starting to leak. If the tick gets louder under power. Again a nuisance but not alarming.