Metal shavings are a sign that something is wearing. I've had them in the rear before, but never the front. If they are big, fingernail clipping size, that is usually not a good sign. Small ones are most probably okay, but I'd check the fluid often, (which can get expensive with RP).
Hmm, it was all "fine shavings" it looked like -- the fluid has an almost metallic sheen to it. Nothing big, but lots of little stuff.
I've still got 4QT of RP left, so I'm not sweating checking it a few more times for the next couple of months. If it has a bunch of metal next month, I'll pull the cover off and see if anything obvious is wrong. Wonder if they'd cover that under warranty....
I run Mobil 1 75W140 in the rear and it seems to stand up better to the heat, as the rear diff gets pretty hot.
I did run RP in both diffs, but it leaked passed the front axle seals quite a bit. So I switched to 80W90 dino in the front and M1 75W140 in the rear.
Dino oil tends to go black pretty fast in diffs, especially in the rear one. I've got 12k on the M1 in the rear and it is still nice and clean. The front tends to stay pretty clean anyway as it isn't do much work. Dino 80W90 was going black in a few thousand miles, in the rear.
If you are lifted you will want to add more fluid than stock as your pinions will be rotated up, and you want to make they get plenty of lubrication.
This has me wondering now, I have 2.5" of lift, and when I took the fill plugs out fluid came pouring out for a couple of minutes on the front (I presume from the added water), and for about a minute on the rear. I filled them up until fluid came out of the fill plug. I guess getting new diff covers is about the only logical answer to adding more fluid than that, heh.
I'll check the axle seals after this weekend's trip, and see if I get any leaking there. I noticed that my front diff seemed to weep a bit of fluid around the bolts at the bottom when wheeling (with stock fluid), not enough to get worried about, but I'll have to keep an eye out and see if the RP makes it worse. (It would appear darker around a few bolts, and wiping it revealed an oily substance, not like drops of it, just a light coating on the flange of the cover.)