I've had an intermittant squeek with mine for a few months now...then I finally felt the right rear hat was warm. So, add this on top of the parking brakes not always working right...I finally took it apart.
The backing plate for the parking brake shoes is rusted out. I got a new part ordered...at my father-in-laws price of $110...Part guy said this is a common thing for these trucks.
Hopefully this will take care of it for another 5 years...at least on the one side.
But check the pins too...they can get gummed/rusted/corroded up and stop working proplerly. And yes, there are slide pins...the caliper has to be able to float to apply pressure to both pads and to compisate for wear.