[Frankie4Fingers]

I don't know where the valving that controls the air suspension is located on your '98 . On my '86 the valves are in the right engine compartment,  forward bulkhead . Yours should be accessible, you can listen ,spray with soapy water to look for leaks .
Are you switching to travel mode before driving ? 
It could be automatic on your coach .
I have a switch that puts it in manual leveling mode .

Ok, so there might be a way to access the valves without going under the vehicle?

I don't know yet whether drive mode will keep the rear up some.  I will check before I leave.  Right now, I know for sure that it lowers itself in the back even if I lift it up manually.  The mud flap was off the ground and then 5 minutes later it is touching the ground and the hitch is almost on the ground.  I also hear air escaping somewhere in the back after manually leveling the rear.

I will give the drive mode a shot to see if it also is too low.  From what I remember on my driving so far, the rear seems to be lower than the front by a ways when I was driving actively, but I will verify the next time I have the engine running.