Sorry, I neglected to address that part of your question.
The instructions says, "It is recommended that the axle lubricant be changed every 7500 mile or as required by your vehicles maintenance schedule"
I think the part in bold supercedes the part that isn't.
In any case, I was told that I could run a severe schedule for my truck according to it's manual. That's 50K, but having fooled around with axles for a while, my opinion is that you would base it upon use. If you tow, you heat the fluid and oxidize it. That dictates a shorter schedule. If you four-wheel or drive in such a way to activate the LS a lot, you may also want to use a severe schedule. FWIW to you, my opinion would be 15-30 K in more severe use and up to 60K for moderate use. I hesitate to run longer than 60K in any axle, though lots of people do. It isn't so much that the oil goes bad, it's just the wear metals that build up i the oil (no filtration at all). It matters to me more than some because I keep stuff forever (still have a truck I bought in '87).
Additionally, my truck has a Mag-Hytec cover, which I installed soon after getting the truck and includes a magnetized dipstick. It's very good for catching the iron break-in stuff. It caught lots of break-in metal as the axle wore in from new but, interestingly, after the Auburn was installed (I used new carrier bearings) not much has been generated. AFAIK, all the materials in the Auburn are ferrous, so should go to the magnet. What that tells me is that there is very little break in matieral to come off, either the new bearings or the Auburn itself. Otherwise I would have advise one short (say 7.5K) run to clear out break in material. Anyway, no problem IMO going 15K or more, assuming you used a decent, brand name i=-mineral oil and don't use the truck terribly hard.
