Toss the PBR pads and put in Textars. Blessed silence.
Aftermarket pads squeal like crazy on rear brakes.
If you are really attached to those pads, pull them, completely clean the slot in the caliper, and coat the rear and sides of the backing plate with antiseize. Put a tiny spot on the contact point of the antirattle spring and the pads, too, as well as where the pins run.
If this doesn't work you are going to have to go back to OEM pads.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!