[Yosemite Sam]

DWayne is exactly right, they can be stubborn.

The front of the plunger is tapered around the outside, I use a very thin pick to clean the "V" shape out.

Then if you are careful and don't squeeze too hard, you can clamp it with a pair of curved jaw vice grips, bigger jaw inside the center hole (where the ball goes) and the smaller jaw on the tapered part.

Then twist and pull. If it's stuck very bad, more twisting than pulling.

If the trans-axle is still in the tractor, to prevent losing the fluid, I will "stand the tractor on end" using a chain hoist.