On my 1995 I changed to Mobil One Syn 90W at 18,000 miles on the open (no anti-spin) 9.25,
then changed it again at 40,000 with Mobil One Syn 90W,
and yet the 9.25 differential was howling so bad at 60,000 miles
that it was torn down and the
pinion bearings,
seals,
ring and pinion and
a re-designed nut with pre-applied factory white Locktite paste was used,
but the differential failed again at 140,000 miles,
even with gear oil changes every 20,000 miles.

Throughout the 1990s Chrysler had problems with the 9.25 that were not present in the late 1980s,
and I have not seen any evidence yet that the root problem has been solved,
even after the independent company American Axle entered the supply train picture.

My guesses:
either the "crush sleeve", or
the locking method to hold torque setting for the big nut,
... are the root of the problem