Still yet to test out my rebuild Mk 2 Jag diff but my Jag specialist fellow Evan Foley (03 9888 8089) said to run for about 500kms on a fairly standard diff
oil through the early wear period and then drain and replace with a true
synthetic oil.
I've an empty container in my shed of the
synthetic stuff he recommends, it's something like $50 a litre I think but he said replace this
oil only every 10,000km having only done top ups in between if required. I can let you know the brand when I get home at end of week but the supplier is based in Dandenong.
You premature wear has to be caused by something else more dramatic for it to happen so quickly.