First time I did mine it was incredibly hard. Over a period of 3 weeks I tried all sorts of devices including a pickle fork without success, Maybe I was just too shy with the big hammer :-(
Finally got it with a puller tool a fellow C3'er had made especially for this job.
From what I learned that time, when I had to do it a second time I simply did it with the
control valve in situ on the car. Just popped off the two hoses from the end,
followed by the adjuster nut, and then undid the two bolts which hold the two halves
of the valve together. which enables you to remove the hydraulics half containing the
spools and the seals. So much easier ! From there you can still also dismantle the other
half and give it a clean out as well if you wish. Once you unscrew the retainer ring the cups just
come apart and release the pitman arm stud/ball end which sits between the cups.
Only thing to watch during reassembly is to take particular care to ensure the stud/ball
and cups are all properly centred/mated with respect to each other so no inadvertent play
is left in there. Otherwise the castellated locking ring won't screw down fully to where it
need to be.
There's a grease nipple on my control valve. I have learned (the hard way) to only use this
during reassembly of the cups & ball and then never again. This is why I had to redo mine a
second time... exuberant greasing of the control valve through the nipple at 6 monthly
regular maintenance intervals results in seals leaking again. Ho hum...
Anyway each to their own, but I'll never bother seperating the pitman arm from its stud/ball
again.