knock in the oil pan

I have an 04 LB7 and just last month I heard sort of a knocking sound that became loader after a week. Worried, I removed the serp belt and listened. The knock disappeared. Now I knew the knock was not internal. Turned out to be the vacuum pump. (covered by warrentee)

Thanks for the info I'll give that a try this weekend. Anyone have any other ideas?

use the old screwdriver method. Put the metal end of the screwdriver against the oil pan and put the other end to your ear and you should be able to tell whether or not thats where its coming from.