WHAT VEHICLE??? WHAT BRAKE OPTION CODE? (JB5???)
ABS is not "junk". It's just not easy to bleed properly. The leading/trailing shoe rear brakes are "junk".
Of course your ABS is a "hydraulic unit".
If this is a '94 K1500 as your user name suggests, you've got the EBC4 controller, and the horrible 254mm (10-inch) Leading/Trailing shoe drums in back. Are you CERTAIN that the master is properly bled? If it's tilted "up" in front, there's a fair chance you've got a bubble of air at the high point that will never bleed out until you remove the master from the booster, (don't remove the brake tubes) tip the front "down", and tickle the primary piston with a wood dowel or Philips screwdriver. You'd then see air bubbles coming up from the master cylinder into the attached reservoir if there was air in the cylinder.
1. Pull the drums off, adjust the brakes. Make sure the park brake cable isn't overly-tight, first. Then adjust the service brakes. Adjust the park brake, if needed, AFTER the service brakes are correct. Start using your park brake every time you shut off the engine.
2. Follow the service procedure .pdf I posted earlier for bleeding the EBC4 controller. You're gonna need a gallon of fluid, a scan tool, and three "special tools". Some guys cheat, and use the "Youtube" process: after opening the bleed valves, they have a helper step on the brake pedal while they remove the rubber cover and then poke the tiny valve that sticks out. Apparently this works for the EBC4; I couldn't get it to work for the EBC310. Others stab the brake pedal on gravel to exercise the ABS; and then bleed at the wheels. Again, if you don't activate ALL THREE ABS CHANNELS you're potentially leaving air in the ABS unit.
