So I upgraded my rear brake cylinders to the 1 ton chevy. Both rear brake lines of course broke while removing them so I replaced the lines and put the new cylinders in. Took a long time to get air out of the lines. Eventually disconnecting the battery got them slightly stiff. Currently when I press the brake the first time its soft to a little above the floor. But if I depress the pedal again quickly the pedal is hard half way like it use to be. The only thing I noticed is that when I come to a stop the rear brakes I can hear are grinding. Any ideas?

 

I'd start by pulling the rears back off and inspecting for the grinding issue, then re bleed.

 

Agree with Mr. Keaton... Need to pull the drums, and see what things look like in there. Were the shoes worn to the rivets by any chance??? Drums rusty? Scored?

Your pedal issue is, I think, just an adjustment issue. Need to tighten up the rears a bit. Inspect first.

 

There is also the rear drum adjustment listed in the FSM. It basically states that you need to ball-park the adjustment with the adjuster then back up 8-10 times, each time coming to a full and complete stop. It is very specific on the full stop thing.