This happened to me on my new to me '89 d250, some yahoo had put the same self-adjuster on both sides. One side would adjust normally one would loosen!!
So yeah a service manual and take photos of both sides before you touch anything! And drum brake tools aren't expensive and make the job a lot easier, get some!
I have to disagree. If a previous owner/shade tree mechanic had put the parts together wrong, the sample is corrupt. Factory service manual is the best advise. First/best tool too.
