'87 4000 Quattro CLUNK!

[Jon Blake]

Others may well have answered your plea about 4ks differential "slop". I
just finished installing a new center carrier bearing. When doing that I
found the CVs at either end of the driveshaft not exactly dry but then not
as lubricated as I would wish. I suggest as an almost free test that you
repack those joints.

And, yes, my driveshaft has a fair amount of play when going from one
driection to the other.

HTH - jon