rear brake clicks on driver side when backing up
 

My 2017 Thor Freedom Elite is on a Ford E450 chassis. The rig has only 6000 original miles, so I don't expect the brakes to be worn.
Yesterday, after a 100 mile trip of mostly Interstate highway driving, I started to hear a grinding sound from the rear axle when braking.
Then, when I backed into my driveway, I heard a loud Click, Click, Click -- about one click every 6 inches -- coming from the dualie on the driver side.
The left hub was not any hotter than the right hub.
I'm not a bad mechanic, but I don't have the tools to remove the wheel.
The parking brake is fully released.

Questions:

Since you don't know how long it has been that way, what is another 12 miles ?

I would check the wheel lug nuts to make sure they are not loose..If they were , that is a different story and you should not drive it until the studs are checked and confirmed safe.