Unless you have a Kubota engine under the hood, it just sounds like a thrashy valve train to me.

Open the oil filler cap and look in there with a flashlight while the engine is running and make sure you have a good flow up there.

If it were mine, I would run the new oil to 3,000 miles so it is not a waste. Then go back to 5W30 dino or Mobil 1, your choice, with a WIX filter. And drive it.

 

Thanks for the advice guys, I am not capable of doing myself bit I am leaving with a shop while I am on vacation to work on my uneven lift and install new motor and trans mounts, if it needs bearings can I get done for under $400? Any more than that and it wouldnt seem worth it, Im all in on the truck but dont want to dump too much into an engine that I could be putting towards a futurerebuild. Make sense or no?

 

That's the exact same sound.

Wouldnt a rod knock be there all the time? My noise goes away when warmed up.

 

I still stand by my earlier post.

I wouldn't open up an old engine just to throw in some bearings. Do it all or don't do any of it at this point.

 

rods knocking can actually make a much quieter to no sound hardly at all when driving down the road, but at idle you will hear our. Fyi it let this fool you because there is engine damage

 

Rod knock usually gets louder as engine warms up. Rod knock can be heard under light load like cruising at 55. There are other things in an engine full of heavy reciprocating parts that can make noise. unplug one fuel injector at a time to see if you can pin point to a cylinder. Hard to tell from a video but that don't sound like rod knock to me.

 

My 2000 has made that noise since about 2009. The stealership has never mentioned it and neither have the guys in the local wrangler club when I get to go out with them, then again their engines make all sorts of odd, to me, noises.

 

That's a pretty common 4.0 sound, pretty much standard when they get some miles it seems. IMHO it isn't bearings, nor is it rod knock. More likely valvetrain related.
I almost never disagree with Bigbadon, but I think piston slap is possible. Tough to tell from the video and my crummy PC speakers.
Some of these 4.0's get so sloppy they bust a chunk off of the piston skirt from the repeated impact.

 

Mine is the same as well. It sounds like a Cummins at cold start, and after warm up sounds healthy. Also just like the OP stated you can still hear from underneath. Me and another buddy (we are both mechanics) are stuck between valvetrain noise or rod knock. Either way with 250,xxx on the clock I drive her every day. Slowly putting some money together for a motor.

 

That oil pressure seems low compared to what mine runs. Is that with 10/30?

 

No that was Mobil 1 Synthetic 10w40.

Right now with new oil pump and Valvoline dino 5w30 it sits at around 13 at hot idle and 30-40 while driving. I am going to try and switch out the sending unit at some point, either way with a new oil pump whatever the real PSI is there isn't much else I can do besides the pump which I just did right?

I think I agree with the it doesn't really matter what the noise is because it isn't worth trying to fix at this point opinion. I will drive her unless something worse happens.

For the sending unit I just unscrew the old and screw in the new when I change the oil? The one I ordered says the threads already have sealant on them.

 

Theres your first problem, synthetic is good oil but it will let you hear every little noise your.4.0 makes.

 

Not unusual for pressure to be a little lower with synthetic. It just means your oil is less restrictive....which is a good thing. 13psi is on the low end of spec but still adequate. OP said it had the famous 0331 crack. That scenario can take a toll on the valve train since it is in direct flow of CONCENTRATED leaking coolant. Lifter/bores and camshaft bearings on cylinders 3&4 take a direct bath.

 

So I ran to Autozone and got a new Duralast sending unit, popped it on and instead of ranging from 13-40 psi with existing unit it now reads anywhere from 0 (with check gauge light) to 20 psi, which do I believe? I know the answer, check with a mechanical gauge....

Is it possible I got the wrong part? Is this for the light and not the gauge? It is labeled "PS401 Switch Interruptor".

On website it says:

"When the oil pressure is either high or low it will either turn the oil light "on" in the dash or move the gauge to the extremes Undetected high or low oil pressure can result in internal engine damage and/or gasket leakage Designed to meet or exceed OE specifications in form, fit and function Global coverage for import and/or domestic applications."

 

I would tend to agree, but bearings can be done in your driveway. You can drop your oil pan and slide new ones in. At this point its worth a shot, but he needs to find 1. if the bearings are even bad, and 2. what caused them to do bad. Either way, its going to be some work and if he can't do it himself, then he should look into other options.

FYI, mine too read 10-13psi when I got that same noise. Whatever you do, just baby it... don't drop the hammer like I did.. your rod will form an escape route through the block.