Hey you-all thanks for the suggestions. But maybe its not really the CV joint. My gut feeling is that it is something else. This loud noise can happen at real low speed if the wheel is jacked hard enough. And then it Un-clunks if you put in reverse and then slam on the brakes keeping wheel jacked hard. Whatever is slipping and clunking is moving back and forth when the steering is stretched out in a certain way.
Now it is true that the CV joint will be stressed in this exercise, but this clunk is substantial--you can feel it with your foot. I don't think the CV joint can clunk like that.
How can I assess the stabilizer bar bushing and clamp? I suppose I could take the bar off the car and drive the car without it on my street just to see if the clunk is gone. Might be the only way, yes? If the bushing and bar are clunking arround inside the bracket there's no way I could see evidence of movement with bar in the bracket and on the car.
How does this sound as a strategy?