Weird sound in engine every few seconds

I’d be running a stethoscope all over that thing to try to pin point it. Check everything even the oil filter for noise.

 

Don’t know. But nothing is impossible. You said oil psi dropped since last change. Maybe there is an odd chance the filter element may be loose inside. Highly unlikely but nothing would surprise me.
That being said what I meant was check everything no matter how small or stupid you think it may be.
Just an example. One one of my old rrucks I had a rattle noise like when a HVAC squirrel cage on a blower motor catches leaves and blows them around. It sounded like it was in the dash most of the time but the motor wasn’t on. It was random mostly happened at idle or in lower gears under 20 mph. So I’m thinking engine is coming apart because Last time I changed oil I found a small piece of piston ring at the plug. Engine runs strong and was overhauled 30 years ago in a field under not the greatest conditions so I figured it was a piece that was not seen and cleaned out at the time and it finally made its way down to the pan. BUT still was in the back of my mind.

turned out to be a shop rag left in the clutch housing that was full of old hardened grease. It was shredded but would get picked up and thrown around in there from time to time. Never gave any clutch problems either.

 

Sounds wrist-pin loose.
Had a company truck years ago with 60 series.
Petro in OKC guard motioned me in and not to stop for ticket because it looked like it was on fire.
That was 50-60 miles after it started knocking, pulling a load of steel.

When I shut it down, it never hit another lick.
They pulled me another truck and took it back and had to rebuild motor.


What it sounded like in the truck driving was the fan was hitting something, I called company and they said just drive it.
It didn’t make it far.

 

I'm not sure. Those guys I tagged are our resident mechanics. But you can hear something coming loose and thrashing around.

Could be a keeper, just the coating of a thrust washer peeling off. But it's something mechanical.