Originally Posted by HoughMade
There is nothing in the crank itself or the bottom bracket that determines whether you freewheel or not (absent specialized parts). That is completely a function of the rear hub which is where it sounds like your trouble is. As the two are connected with the chain, it would make sense that you hear and feel something from the crank.
Yes, it seems to be coming from the rear hub. When I did the build, I removed the shifter and converted it to a single speed, just to make everything simpler. But, I've had to keep the chain very tight in order to prevent it from jumping across gears. I'm wondering if the chain being to tight could have caused some damage to the bearings in the hub.