1998 GMC Truck REMOVAL OF BRAKE DRUMS

I'm sure you already did the job, but here goes. There should be one or two slots in the rear backing plates with little rubber plugs. Pull out the plug, look inside with a light, push a screwdriver against the flat looking steel plate, push it away from the geared wheel, and turn the geared wheel with either a flat screw driver, or a brake adjusting tool until the drum spins freely. The drum should come off.