Had to replace 2 x 40 x 40cm fence posts today. First one came out OK after the usual application of brute force & ignorance.
Second one was a pig. Tried everything, dug down 2' and it still wouldn't come out. The only option left was to cut the bugger down as low as possible. I could still bury the new post 22" below ground level, so out came the Titan el cheapo reciprocating saw.
Drilled a hole centrally in the post stub & started to cut. Got through from one side & low & behold, the stub started to move about in the hole. The vibration from the recip saw had loosened it sufficiently for me to simply pull the stub out vertically.
Now thinking of making up an adaptor to utilise just the back & forth action.