Truck is a generation one GMC Topkick, 1981 model. It is a over-center bucket truck and has drum brakes, Bud 20" wheels. It has a Mico brake lock system, which is a system that locks the brakes in the applied mode, and releases by pressing the pedal and activating the release. The truck was parked in a parking lot in Baton Rouge LA and apparently, the Mico brake lock was applied. When I picked the truck up, two brakes were frozen, right front and Left-rear. Right front broke loose easily, but that left rear will not loosen. I bled both wheel cylinders on the Left-rear but it appears the pads are froze and rusted to the drum. Don't believe the r-front is part of the Mico brake system, only the rears. Also unsure whether the Mico Brake uses both wheel cylinders on the drum, or just one. Here is what I have tried so far: I jacked the left rear duals up about 2", and the truck is still on my trailer, and the right rear is chained down tight, and the truck is chained at all four corners in 30 degree tie down. Fired the truck up, put it in reverse and popped the clutch trying to break it loose. It spun the right rear dual... My next move will be to pull the tires on the left rear, and drop the LR onto shoring material wood blocks. I will then chain the RR to the trailer. Then I am going to take the pressure washer and blast the drum, and try popping the clutch again in reverse, So now for the question. Any better suggestions on how to break the shoes loose from the drum?