Maybe a month ago I noticed a faint random rattle I thought was coming from the 5 speed in my 04 4.8 Silverado. It would come and go with no pattern. It started to become much louder and more consistant so I parked it. I drove it last weekend and the rattle is louder now and constant. It sounded like maybe a loose nut being kicked around the bell housing. I pulled the transmission yesterday and nothing looked abnormal. I pulled the clutch set and all looked fine. With the transmission and clutch set seperated from the engine, I started the truck and it still rattles. It definitely sounded like a loose nut just rattling around in the oil pan. The speed of the rattle will increase and decrease with the RPM. It's just a random pattern to the rattle though. I pulled the oil pan, oil pump pickup, and windage tray. The oil came out clean as oil that needed changing. No metal that I can see in the pan. Nothing looks out of the ordinary on the bottom end. I was expecting loose connecting rod or something but everything looks normal. Any ideas y'all?

 

check your lifters.. could have collapsed a spring

 

I'll check out the valve springs. Definitely coming from the bottom end though. Probably should have noted in original post as well that oil pressure is normal, temp runs good, truck drives well. It's why I first thought it was the transmission.

 

yea not thinking its a valve spring but a LIFTER spring.. it can sound like its bottom end

 

Wow, it's too early I suppose. You did say lifter. What would be the best way to troubleshoot a bad lifter? I hate throwing parts at problems.

 

fastest way is pull the intake manifold and look.. but you can pull the valve covers and check each pushrod and make sure theres no play in them.. if you have one with excessive play then its def a lifter.

 

Passenger side catalytic converter was the root cause. Not sure why I couldn't pin point it before all that even with my head right under it. Got some new gaskets and a thorough engine flush out of the deal at least so not a bad deal. Just glad it wasn't anything bad and it's back on the road. Now to flush the mud from the clutch and find out why the AC only blows hot now.