This could become a very dumb question.

I looked at the big FJ board, FSM, Google, here and through the inspection cover in the rear door, but can't tell how the rear washer gets it's fluid. Does it feed off the main underhood tank or have it's own? Do I need to refill it? If so, how?

I'm thinking it might tap off the main tank since I use it a lot during rainy season but haven't refilled it ever in almost 4 years.

 

yes.

 

Hi Bob, yep.
There is a hose underneath that feeds it clear to the back.
One nice thing is we have a huge tank up front for it.

 

OK, thanks. That answers why the tank is the size of a small aquarium.