Just unscrewed the nut to take out the ceramic cartridge from my
shower mixer. I'm pretty sure the brass nut and ceramic internals
should be a single removable unit. But the nut came off and left the
whole ceramic assembly firmly fixed in the brass body of the unit. I
haven't yet tried applying force to remove the remains of the
cartridge, though finger pressure won't budge it in the least.

If it does need some welly to get it out, I'm wondering how easily the
replacement will slide into place. I guess the cartridge body needs to
be able to rotate as the integral nut is tightened. So whatever is
causing the old cartridge to resist extraction may make inserting the
new one difficult.

If it turns out there is some resistance, is it ok to use a grease,
such as Vasaline for instance, on the combined ceramic and brass
parts?

--
Regards,
Dick Treen