Back in Dec of 2000 I bought a new 01 Grand Cherokee.
Within a few weeks the rear-end started to make noises around corners. The dealer told me that a few of those got out of the factory without the additive which makes the oil breakdown very fast and that was probably what happened to mine.
I caught it very early (1st day it made noise) so when they opened it up to check everything there was no damage and all tolerances were still within spec.
The fluid was changed to synthetic at that time and they added 2 bottles of the additive. That solved the problem, no noise since and the Jeep now has about 68,000 KM.
I am not a mechanic but I would suggest you put the additive in to be safe.
Ken