Forcefully Attempt Stubborn Extension Separation

What happens here

Shifting from explanation, the mechanic is seen vigorously hitting the axle extension with a large hammer, attempting to separate it from the main axle. He verbally expresses his confusion and frustration, stating, 'I don't remember how I got this apart' and lamenting that the piece 'totally should spin free.' The repeated and forceful hammering indicates significant resistance from the stuck component.

Goal: The mechanic then uses a large hammer to try and force the extension piece off the axle, expressing frustration that it should be easily detachable but is not.