I cleaned the #2 post in my 1981 US 5-speed last weekend without removing the entire quarter panel.
Steps:
- Remove toolkit cover
- Remove rear carpet
- Disconnect ground strap
- Remove the passenger-rear side luggage cover hook (2 screws)
- Remove two trim screws from the quarter panel where it attaches to the body almost behind the toolkit cover
- Remove the single screw that holds the panel down to the hatch area floor - on my car, this looked like a wiring bundle tie-down, but was also an attach point for the quarter panel
At this point, I was able to pop the quarter panel end out a couple of inches. This involved popping loose a couple of the trim posts that attach the panel below the rear window.
I could then fit my hand behind the panel through all of the soundproofing to get to the ground point bolt. I used a 10mm combination wrench and a LOT of time to remove the bolt.
Pull the ground wires back to the rear of the car to clean. I got lucky on the install and the bolt threaded properly the first time.
I took about an hour to do this. Turning the bolt with the wrench in these close quarters was extremely tedious and roughed up my hands quite a bit.
Good luck & be careful with this panel! I was rougher with it than I wanted to be but I managed not to break anything.