Chup,
I would not know, so I Goggled to try to find an answer. Here is one that applies to a vehicle, but could answer your question for the tractor. They used a sledgehammer , so it would appear you would be OK. But here is the URL and maybe it helps.
How to Separate Frozen Ball Joints | eHow.com
Here is an extract form this link:
#2...
Pull the cotter pin out of the upper control arm ball joint with the needle-nose pliers, then unbolt the upper control arm ball joint nut from the upper control arm with an open-end wrench. Spray the penetrating spray in the gap between the ball joint and the steering knuckle.
# 3
Strike the side of the steering knuckle with the sledgehammer to attempt to wedge the ball joint free from the steering knuckle. Attempt this several times and if it does not break free, then proceed to the next step.
# 4
Insert the pickle fork between the upper control arm ball joint and the steering knuckle. Strike the end of the pickle fork with the sledgehammer to try to wedge the pickle fork between the ball joint and the steering knuckle, breaking the two apart. Attempt this several times, and if it doesn't work, proceed to the next step.
# 5
Install the pickle fork attachment to the air hammer and the air hammer to the air compressor. Insert the pickle fork into the suspension just like you did in step 4, but now pull the trigger on the air hammer to push the pickle fork forward. Do this until the ball joint separates.
Read more: How to Separate Frozen Ball Joints | eHow.com
How to Separate Frozen Ball Joints | eHow.com
Jim