If the weather holds out tomorrow I'll jump back in to see if I can spot something. Thanks for the replies all.

It sounds like lifters knocking. My 96 xj does it sometimes on cold start-ups. If the noise goes away, I wouldn't worry about it too much. Just make sure your oil is clean and full. Also, have you used a real oil pressure gauge or are you going off your dash?

Do you think I would hear the lifters in the bottom end as opposed to the top end? I was just using the idiot gauge on the dash

Little bit of a follow up. I pulled each spark plug wire to see if a load change on each cylinder had an affect on the noise I'm hearing in the oil pan. Didn't change a thing. I'm hoping that's a good thing considering it may not be bottom end related.

I did notice the second cylinder from the firewall has a lifter sticking on cold start up. I can hear it tap, tap, tap then fade away only to come back a few seconds later. I'm going to pull the valve cover tomorrow to see what's going on in there. I'm not sure if this problem is related but I'll try anything at this point.

Sounds like a cracked flex plate to me.

I've yet to look over the flex plate w a fine tooth comb but that's next on the list. I just don't understand why it would quiet down with heat.

On a side note, valves, rockers, rods look fine.

Metal expands when its warm. Cracks will "close" with warmth.

Had the same noise, ended up being the flex plate being loose.loc tight & tightened the 4 bolts still no issue 2 weeks later :-)

I guess this would be a good time to update my post.

I was hoping the noise was coming from the Flex plate so I had taken off the cover and loosened/re tightened with no change. They were all pretty tight to begin with so I sort of knew it wasn't going to be the issue. That was about a month ago.

I've been driving with this noise for about 15K miles now and it has worsened pretty drastically throughout that time frame.

At one point I almost bought the materials to replace the rod and main bearings but lost motivation and just decided to save up for a crate. I figured it would be a test of time to see how long I could actually go with the Jeep sounding like a full blown diesel until it grenaded.

Today in a ditch effort and because I was bored. I bought a can (1 pint) of seafoam from autozone on lunch break. Ran about a half a can through the intake manifold and dumped the rest in the gas tank. On restart, would you believe the noise is COMPLETELY gone? Holy sh1t. I kid you not my cherokee sounded like a diesel engine and now.......not a sound. The only explanation I can think of is carbon build up on the piston heads?

I hope this isn't just temporary. I can't even stress enough how relieved I am with the sound of my 4.0 now.

Piston slap, my engine makes the exact same sound. I had someone look at the lower end of my engine a while ago, they said it was just piston slap and maybe a worn wrist pin on my #6 cylinder. It goes away for a while when I run stuff like seafoam. Don't worry about it, this is COMPLETELY normal for the 242 (Not saying it's meant to do this, it's just they all do it). Mine's been doing it for 4 years.

Skip to about 1:25. I got lifter tap and cracked exhaust header mixed in there as well.

Forgot to add this on. Try different brands of oil and see which one the engine likes best and run a good oil filter like Wix, Mopar, or Napa. The 4.0 is a picky beast, but keep it pleased and she'll take care of you.