Slide doesn't stay tight to frame when driving the MH

It says that coach air pressure needs to be up to snuff. Ride height isn't mentioned, and I can extend/retract the slides either sitting on all 6 or on the jacks.
I guess the way to test the low fluid possibility is to add fluid to the reservoir and take the coach a couple hundred miles up the road without having the support bracket installed.

No procedure that I found about purging air, but looks like I can add over a pint of ATF and not come close to over-flowing. No "ADD" or "FULL" marks on the tank...