and not needed if you use a good quality diff oil as they already contain sulphur EP compounds (or better still borate esters in some) that also prevent metal to metal contact in high speed/high load/high heat conditions.
Generally, Moly-di-sulphide is a no-no with rolling element bearings.
Moly is brilliant in low speed/high load areas where boundary lubrication may be needed. (eg. sliding splines, CV's)
Our Patrol has done 400,000km now and used mostly for towing and the rear diff makes no sounds and it still has the original bearings and seals.
It's only used premium diff oils since new, no additives.

