Warren Block said:
Both the LJ4000 and 4050 have the same self-test page showing a toner
available estimate. I've read that the C4127X toner will also work in
the LJ4100, but have never tried that.
The LJ4000's I have have a different self-test page to the 4050, I don't have
an explanation for that unless it is to do with year of manufacture. My service
manual confirms this.
The LJ4100 and 4000 cartridges differ in two respects, the 4100 cartridges have
two extra contacts which are to do with toner level reporting (I think) and not
of any real consequence. The other difference is subtle but important, there is
a different gear on the end of the drum, one of them has one extra tooth (from
memory 51 for the 4000 and 52 for the 4100, but I could be 1 tooth out), this
means that although the cartridges fit both printers there is a risk (prabably
a certainty over time) that damage will be done, for this reason I do not
recommend using the 4000 cart in a 4100 or the other way round). I have put a
4100 cart in a 4050 for very short periods (for testing) and can confirm that
it works but I can't say how long it would last.
Tony