I have a 2001 Yukon Denali with the 6.0L and a few months ago I lost oil pressure and it began making a noise in the engine that sounds like a collapsed lifter. The truck only has 66k miles on it. I've had it to two different shops and both said I need a new motor. The second shop I took it to replaced all 16 lifters and put in a meling high volume oil pump. The rod bearings were checked and were in great shape. After it got new lifters and an oil pump, the oil pressure comes up(only to 20psi cold and 10psi hot) and still has the "lifter noise". A couple different people told me to check the oil gallery plugs to make sure one did not back out or come out all together. Anyone have any ideas? Please let me know. I've been without my Denali for 6 months now!

Worn cam bearings and/or mains can cause this, putting in a new pump will not correct the source of the problem, the engine must be "dug" into further. I would check with a dealer to see if there is a common problem with this engine that might help pinpoint the issue.