Crawled under coach to drain tranny so I could fill it up with Transysnd. Pan drain rain plug --no problem--3/8 drive worked fine. Took a 9/16 and a 5/8 socket under with me in anticipation of changing the filters.
Nope. You guessed it.
15mm.

I can get under the coach and back just fine. It's my fat butt and belly that has the problem.