Reading other responses to wiring detached garage, most replies suggest grounding rod, in addition to the ground wire that is from the Main panel. My garage sub-panel does not have a grounding rod, I would like to get some information on installing one. Is there a minimum distance from the main panel grounding rod to the sub-panel grounding rod? Do I just drive the new rod into the ground and attach it to the ground bar, that is, by the way, isolated from the neutral bar, in the sub-panel? Thanks for your help.

Any two ground rods must be at least 6 feet away from each other.

Simply drive the rod, and connect to the equipment ground bar using min of #6 copper wire. All 8 feet must be in the ground, use a ground rod wire connector that is rated for direct burial.

Why does it sound like the rod existing for the main service will be close to the rod for the garage panel?

I either heard or read there was a minimum distance, but could not remember. The two rods will be near 60' apart.