So I'm not seeing how to get more slack so I can slide the sprocket off futher. I loosened the guide rail on the right, and would like to loosen the banana rail on the left, but don't see how. I have read (maybe) about pushing that back through to the left, but that it's racheting so I'll have to pull it all the way out and go back in from the right. I must be getting confused, because I'm not seeing how that's possible. Someone clear up what I'm seeing in there please?

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1981 300D 205,000 mi.