Something to add to what I posted above, and relates to ultrarunner said. If it is the older style 580CK with the old style dry disc brakes, the steel balls in the expander plates get pretty rusty & gnarly. They will after time get somewhat of a flat spot, or a circle groove in them from seating in the grooves they ride in. I have cleaned some that weren't too bad, and replaced others when they were beyond hope.
I replaced the balls & springs in my 480C several years ago. Got my parts here:
Remanufactured Transmissions, Torque Converters, Engines - Joseph Industries Thinking the springs (takes 2) were less than a couple bucks apiece, and the 7/8" steel balls (takes 3) were right at a buck apiece. They beat everyone hands down on prices on everything I needed. Granted, they are aftermarket parts, but do seem to be high quality on everything I've ordered through them.
IF you decide to remove the brake assy., do know the two bottom bolts holding the brake assy. on, the holes for the bolts go clear through the side of the diff. housing. When you back them out, diff. oil will drain out. So you'll need to drain it down some.
I'm not sure when they started putting them on, but my 480 has the Case version of an automatic brake adjuster. Thinking they did this when they introduced the hydraulic brake systems. I know my old 310B which had strictly manual brakes, did not have that feature, although pretty much the same brake housing.
On the bright side. If the brakes are grabbing, that's usually a good sign the seal is still good on the bull pinion shaft the brake discs ride on. If it's bad, stepping on the brake pedal is somewhat like stepping on a Plum, and little braking action going on...
