The problem with the auto adjusters on these trucks is that the teeth on the wheel have such large steps, that by the time the adjuster actually works, the shoes have worn down to create the problem that you have just gone through.
Now I feel like the dumb-ass for not having thought about this sooner to point it out! I actually DID know this!!! Monkey muffins! DOH! Lol!
I don't rely on those adjusters! Cycling the E-brake a few times, which is supposed to work...doesn't!
Driving in reverse & then hammering the brakes, which is also supposed to ratchet up those adjusters, doesn't do it either!
To top it off, GM in their infinite wisdom, provided no windows on the back of the backing plates to be able to adjust the brakes without having to remove the wheels & the drums! SMH!
Disc-conversion, disc conversion, disc conversion!!! Just from a maintenance point of view, is the only answer!