Brake Issue, Passenger Rear Brake Frozen on Take-off

[lts70]

On my 70 Chevy I have noticed that the rear passenger tire/wheel is locked up when I first get going in the morning. It feels like the rear parking brake is on for that side. It only lasts on my initial take off then goes away. After the truck has sat over night or when I get done with work it happens again. Once I get going and even come to a complete stop again it does not happen again and acks completely normal on take-off until the truck has sat parked for awhile. It does not occur when I go in reverse only when I go forward. I can back out of my drive way just fine and then when I go to go forward it takes more gas to overcome the friction and I can feel the bind until I get moving. On gravel it will even drag a bit before it breaks free. It has happened for the last few days each day getting a little more aggressive. I am going to pull this apart tonight and take a look. I was wondering if anyone has any suggestions of what to look for. I am thinking it must be a bad self adjuster or parking brake issue but have never had this happen before so input would be greatly appreciated. I have only had to drive it a half a mile a day as I meet a co worker at a park-an-ride to commute for work, so I hope I have not caused too much damage if something is mangled in there. Next week I have to start driving her 60 miles round trip again so I defiantly need to get this fixed.