I was able to reach back to mine, which is back by the tag, by removing only the outer dual. Jacking and blocking the frame to create space helps. I used a long extension. I imagine no one had ever checked those on my coach since all the others were loose, but the bolts on that small slide were all tight.
I agree that it's a horrible place to have a slide motor that Newmar KNOWS should be checked a couple times a year.
"Second star to the right and straight on 'til morning"
On the Mississippi in SE Minnesota
2013 Newmar Mountain Aire 4336
2016 Chevy Silverado 4x4