The parking brake is just like a regular drum brake but inside the rotor "dome". It has shoes rather than calipers and pads. It is cable rather than hydraulic. If it was freezing out perhaps the following applies........It sounds like some water sloshed in there and then froze later. No need to get rid of it; just don't set parking brake if you don't want to. Rubbing noise may have been ice, frozen shoe, etc.

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The Golden Rule

1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)