Thanks for all the info, everyone!
Reading this thread, I realize I have no idea how air brakes work, I'll have to get to a DMV for a book. My last diesel (23,000 lbs) had hydraulic disk brakes all around, along with Hydroboost by Bendix.
This newer RV I have (26,000 lbs) has air brakes all around. And I know NOTHING about air brakes.
Here's a pic:
Air brakes...And another:
Close up...Yeah, the RV lived in Minnesota for a while so the dreaded salt roads made things look bad under there. Everything works fine.
Thanks to this thread, at least I have a drawing now...