Air compressor, dryer, governor, or leak?

I have a 2012 Cascadia DD15 with a 10 speed eaton. 602k miles I brought it in November.

The past few days here in Maryland we have had temps in the low teens overnight and when I start my truck the air pressure will build to 100 psi in both takes and never reach 120 and make the air dryer shoot off. I have let the truck run for hours water temp goes up truck warms up air stays at 100 psi or below.

I try to drive the truck on the low side put it into gear nothing happens no reverse or anything l flip the range selector up to the high nothing. Except I hear air coming from the shifter when on the high side. When you usually change the range you can hear the transmission change from the high to the low side or vice versa.

When the truck finally goes into gear it is stuck on the high side and I have to drive it for a while before it will go back to the low side after the air dryer starts shooting off like it normally does.

When I drain my air tanks I see mist coming out and it seems to be water no oil or anything. I stopped by freightliner and picked up w air dryer canister and will change it in the morning.
What could possibly be my issue and I do I solve it. All help is greatly appreciated.