Tell us about yourself!
I used to tear down and install fences for years. We used to just notch a groove in the post with a circular saw and place the jack (a jack- all) in the groove and pump it out. Sometimes you get lucky and the post breaks free from the concrete and comes right out clean. Then you can put your new post right into the old concrete hole and add some new concrete to the top. Saves a lot of time.Sometimes the post would break so then we wrapped a chain around it and jacked it.. I used a jack-all for all this. They are around $40.00-$50.00 and a good tool to have for a lot of jobs..But Northwind's idea would work great if you had no jack.