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Rear brake shoes work best to keep rear wheel from moving forward, but can barely hold it from moving in reverse.
So I would say from your description that the brake shoes on that wheel are stuck open, pushing against the drum, locking forward movement but allowing some reverse movement.
You will need to check both rear wheel brakes
The passenger side drum will be hard to remove, since "brakes are on"
On the back side of the brake plate, lower down there will be a rubber plug.
Pull out that rubber plug, inside the hole will be a "Star Wheel", this adjusts the brake shoes, and can be used to retract the shoes so the drum can be removed.
You need to use two screwdrivers, one to hold out the Star wheel lock bar, and the other to rotate the star wheel
This article has pictures of whats inside and how to repair it:
http://www.ranger-forums.com/engine-drivetrain-122/how-servicing-rear-drum-brakes-81906/