I have a similar noise, but I only hear it when the emergency brake is engaged.... and I'm pretty sure that I need to adjust the e brake on the rear drivers side.... cuz when I'm pointed up hill on an incline... pull the e brake.... I can feel the passenger side go up, but not the drivers side.
BUT! when the car is parked, with the ebrake, and I get out and push down on the drivers rear corner... I hear some noises.. (never tried it without the ebrake engaged)
Former: 95-530iM
Current: 99 GMC Seirra 1500