Dirty Front Differential Fluid After 800 Miles = Problem?

[det07]

05 Silverado 44,000 miles ...I changed the fluid in my front differential at 43,000 miles. The fluid was a nasty gray color with lots of metal shavings on the plug. I put 80w-90 convential in it and drove 800 miles. The other day I put 75w-90 synthetic in it and the old oil with only 800 miles was almost as nasty as the original w/ lots of metal shavings. Does this indicate a problem? Is water getting in somewhere? The color of the oil is not milky like I would expect if it had water but I was suprised at how dirty it was anyway. Should I change it again after another 500-1000 miles to check it again? If I take it to the dealer what parts will they inspect? Any input is appreciated

[Zembonez]

The new fluid could just be showing remnants of the old fluid, but I'd change it again in say 500 miles to make sure. The shavings spook me a little. If they are still there in the next change, I'd get it checked out before it becomes a major fix.