Spinning castle nut on lower control arm

I am stuck trying to get the passenger side axle out of the tranny,
because the castle nut holding the lower control arm to the ball joint
stud is spinning but not coming off. The nut did come down partially
before refusing to thread any further back on or off though. Right now
the nut covers just about the last couple threads.

I would think it should loosen fairly easily with the the LCA pushing
down on the nut, but I guess not. Any suggestions before I take a
dremel to the nut and risk damaging the threads on the ball joint stud?
I suspect the harder threads on the stud are fine and I'd like to avoid
having to buy a new ball joint.

Lindsay

 

Ok, I just got back under the car, despite it being -7 degrees C out
here. It looks like the nut hasn't even partially come down, as the gap
in the castle nut still lines up with the hole in the stud for the
cotter pin. I suspect the mechanic who replaced the axle at one time
pounded it on with an impact wrench since it is just the last few
threads that are screwed up. Just some new information. Any tips
appreciated, though I may just get impatient and take a dremel and
chisel to the thing pretty soon.

 

Don't be too hasty when you get frustrated, a little patience can save
that frustration from compounding. When I did my axles, I used my jack
to put force upwards on the lower arm. this stopped the ball joint from
turning. The stud is tapered, and jacking up the control arm squishes
the tapered hole in the control arm against the tapered part of the ball
joint stud. It should stop it from moving.

Mark

 

to add to that, yes, put the jack under the arm, but sometimes that's
not enough. if it's real stubborn, have an assistant use a lever to
press the knuckle down against the jack's upward force. that /really/
clamps the taper in the hole & you can then undo it easily.