Sounds like a lifter to me.

But, we need more truck info!

 

2004 6.0 with 130,000 miles. Single owner and maintenance kept up regularly.

 

Ok, that engine did not have DOD/AFM which is good news.

I think it's a lifter.

Can you tell which side it's coming from?

 

Piston slap sounds like a slap and usually goes away as the engine warms.
A lifter can be replace, and there are a number of "tricks" that sometimes can free a collapsed lifter.

Do you have a mechanic you trust?

 

I don’t have a good mechanic at the moment.

 

My 2002 has a slight piston slap when cold and disappears in about 20 seconds. Real quiet after that. GM used short skirt pistons for weight reduction. My understanding is that its caused by carbon build up in the piston ring lands but it doesn't affect the engine according to GM engineers.
Either way if its a lifter noise the heads will have to come off to get to the lifters and if its a wrist pin then the block will need to be inspected and a piston replaced. My question is what caused this. How is the oil pressure at idle and 2k rpm? I suspect that maybe the oil pickup tube o ring may have gone bad and resulted in oil/air cavitation.

 

Replace to O ring on the oil pump. Pull the pan. When there, pull a rod cap 7 or 8 and look over the bearing. If needed a good mechanic at that point can replace all the rod and crank bearings. Check the ream main seal too. Most tapping noise on these motors is caused by the O ring. Go to Napa and get the right stuff gasket sealer in a caulking tube to reseal the pan it is the best stuff. About a 6 hour job on a lift.

 

I think I’m going to pass on the purchase. The vehicle has rust in the rockers which makes me nervous about rusted bolts when attempting a repair. I’m still in the market for a Vortec so this information has been very helpful. Thanks for all your input, I’m sure I’ll be back.

 

I have a noise similar its a ticking sound my truck is on 7 years with low miles very well maintained