When I have the windows down and driving at parking lot speed I hear a tick, tick, tick like you would hear if there was a rock stuck in the tread. The tires don't have enough tread to pick up a rock for one and this truck has never ever been off pavement ever. Its a 2001 F150 4x4 Lariat Crew Cab. Its kept super clean and always greased, and fluids changed every 3-5k miles.

Any thoughts?

 

Check for anything that you may have run over. I have had nails, screws and pieces of metal stuck to, or in tires that didn't cause the tire to go flat.
Hope that helps...

 

Have you checked the u-joints? If they are really worn they will talk like that. jgeese's comment is also correct. Anything on the tire will make that noise.

 

ABS Sensor.