Low-speed "clunk" 1-2 shift, A-904

When my '70 Duster (318/904) was running, I would always have to drive funny at slow speeds (parking lots, etc.) because if I was accelerating really slowly (NOT when accelerating at a more brisk pace), the transmission would make a "clunk" when shifting from 1st to 2nd. Browsing through my FSM I saw the term "low/reverse band adjustment" and "kickdown band adjustment" and purely by the names of those parts I figured they might help me out. When I pulled the pan to replace the filter and fluid (BTW there were a couple tiny pieces of metal, smaller than fingernail size) I adjusted the low/reverse band just because I was under there and figured I might as well, but I haven't got a chance to adjust the kickdown band (and the low/reverse adjustment did almost nothing). Now that the engine is out of the car I figured I could pull the transmission to finally fix that damn fluid leak and adjust the kickdown band. Is this related to the "clunk"? Also, I have barely an inkling of how these (or any auto trans) work, so what exactly do these two "bands" do?