The rear axle has helper air bags, they are great for heavy trucks! I generally run about 70 psi in them, this helps keep the rear end higher, and also off the overload springs. Makes for a better ride with a heavy rear end.
Here you can see the overload springs are not touching the perches with air in the bags.
And here is what it looks like with 0 psi in them.
But when they were installed, the fillers (the air valve like your tires) were installed right on top of the air bags. This meant climbing under the truck and sitting by the rear axle to fill or even just check pressures.
The fittings used are quick connect, so I deflated the bags, and went to work taking the valves off. I used DOT 1/4″ air line to extend them back to the back bumper. Much nicer to be able to check pressures and fill now!
