[Richard]

Front Axle

Do you think it was time for service?
   
   

Here is the manual. 
https://cumberland-companies.com/wp-cont...Manual.pdf

There are a couple of things to be aware. First, you can remove the brake pads without removing the caliper. Easier than a car. While you have the brake pads out ensure the caliper slides freely on its pins. If it doesn’t you have some work to do. Mine did. 

Second, although my slack adjust system was very similar to what is described in the manual, it is different enough to throw a curve ball. Mine would not back out as described in the manual. And I could not find any mechanism to allow it to back out. It would tighten down, but not back out. I took it apart, and found a way to retract the pistons. As you can see from the pics there are two shafts with geared teeth that are connected by a small chain. At the base of that shaft, it’s mounting plate fits into a recess in the caliper. That recess has a tang the prevents the base from rotating. If you will simply pull both those shafts out of the caliper, then you can improvise a tool for retracting each piston. If you have to use this improvised procedure take a straight edge and ensure the pistons are aligned relative to one another. It is possible to cock them, which would cock the pad. Not ideal.

If you need to remove the caliper, the bolt heads are 30 mm and you will need a 1 inch impact gun. Thet are put in with loctite.

And if you need to remove the caliper, remove the two bolts holding the air brake chamber instead of unthreading and twisting the air brake line.