The neighbor and I replaced 7 posts this summer on a section of our fence that had blown over. Here are my thoughts:
1. If your posts are weak where they meet the concrete (as ours were, especially since it had blown over), it's going to make the task worse.
2. Wrapping the chain around the concrete - dig down around the sides of the concrete at least 6 inches and get the chain as far down as possible. The concrete is "bell" shaped, especially at the top. But, it's also weak there and you want most of the tightening force inwards, not upwards on the bell. About half of our posts we had to dig all the way out because the concrete would just crumble when trying to lift.
3. Make a bridge-like structure over the post you're interested in extracting. I used wood blocks, but cinder blocks work too...bridged by a strong plank (basic 2X4 ain't gonna cut it). Use a hook/eye at the end of your chain, wrap it twice around the post if possible, and start jacking. Some came right up. But, as I mentioned, some didn't.
If you pull at an angle (i.e. with a truck), you'll deform your hole. Try to go straight-up if possible.
In the 7 posts & 6 sections we replaced, I would estimate that about half of our time was just getting the posts out. Once the old ones are gone, you know where your holes are going to be so you're ready to start setting new ones.
Let me know if you have questions. Good luck!
