This trick works great to pop a ball joint from an arm or a socket like in a knuckle. It can be used to remove both sides of a ball joint. In this video I demonstrate pulling a Subaru ball joint from the knuckle. Even when very rusty, this works well. It helps to spread the ball joint clamp a bit before attempting. Hope this helps!
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https://www.youtube.com/watch?v=Eph8xyBP3Fc