2005 5.3 Mystery oil leak

[Deeznuts454]

Good afternoon, 

I am attempting to chase down an oil leak on my 2005 Yukon XL with the 5.3. As far as I can tell, it is coming down the back of the block all the way from the top, and is leaving about a baseball-sized puddle on the ground overnight. I have replaced the valve cover gaskets, valley pan gasket, and installed a brand new oil pressure switch. What else could it be?? Could the camshaft position sensor be leaking? 

[Brian715]

I came here to write oil pressure switch, but then I finished reading your post. Seems like a leak that much could be active while running.  Might be worth putting some UV dye in the oil and using a UV light to chase it down. 

[Mikebtte]

Rear oil seal could be leaking. The 5.3 has an oil plug that can leak past and leak. Best to pull the transmission and replace the rear plate and check the plug while you are in the area.

[sefiroxx]

. . . And check valve cover gaskets