Let me try to answer these questions. We are not sure if the brakes worked before it was sent to us from Florida to be going to another one of our other sites. I found that the booster vacuum resouvoir was not connected so we thought that was the problem. I removed the resouvoir and pulled a vacuum with our A/C pump. Pulled and held vacuum so we reconnected. Nothing changed. This is when I suspected the unit had a problem before it got to us since the resouvoir was disconnected.
As far as the pedal, everything is free and connecting rod has just about an 1/8" play before contacting the booster so not to actuate prematurely.
I did not check booster to see if it not leaking because the old booster and new booster are acting the same.
Parking brake is connected to the drive shaft and not associated with the wheel brakes.
As far as the grinding inside the drum that has me scratching my head. The sound we hear sounds like the springs inside the drum are over stretching but the shoes are sitting fairly tight in the drum. I have adjusted multiple times without any change.
Tomorrow I am going to check to see if the breather tube from booster to filter is clear. I assumed it was and I didn't blow thru it when replacing booster so I cannot be 100% certain.
Not sure if I posted this earlier but today I had it running wide open and shifted to neutral then shut down motor and while drifting I applied brakes and it seemed just as bad as when I had vacuum from the pump. I really do not want to have to break these drives down again just to inspect the shoes and associated hardware. BTW the brake lines are steel and it has 2 lines coming from M/C (one to each wheel) and they are in good shape.
Again thanks. Ed