It's between a few things but you bunch should know.

I'm not sure if I have a rod knock, bearings issue, lifter tick... or a mix
Engine on cold start up has decent oil pressure (doesn't cause me any alarm) but has a knock (sounds like it's coming from the bottom/lower end) and goes away after the engine is warming/warmed up. I don't really hear it once it's warmed up (but I think I may still hear some lifter tick, and I hear some tick's are normal in the noisy 4.0L?)After getting the engine oil completely warmed up while sitting stationary my oil pressure drops to a low (but apparently in-range) pressure of 16~18 psi.

I've checked torque converter bolts, all tight.
Never gone past 220 degrees while driving, only after restarting a already hot engine, so it's never overheated in my ownership.
Changed the valve cover gasket and the valve cover looked good, didn't see evidence of sludge.
I've looked into the oil fill cap with engine running and can see oil flowing (just don't know how high it's supposed to be.)

So, do people thing I have a rod knock, bearings issue, lifter issues or a mix of the 3.

Engine runs strong and I don't hear and noises of concern when I hop on the throttle from inside the cab.

Sorry if my terms are redundant.

 

I'd be surprised if you didn't have lifter tick. Some oil filters allow oil to drain out when not running, and it can make some noise until the filter refills.. you might try a wix or mopar filter. Many say fram is bad for that.

 

Hey there Mark...If you have high miles and the pistons and cyls. are worn you may have some piston slap. Theory goes that after a few minutes pistons heat up and expand and then fit a little tighter.

A worn rod might rap a bit immediately when you start it, then quiet down right away as the oil pressure comes up. Then you get a somewhat nauseating, solid knock more or less connected to the gas pedal. Only gets worse if you want to go somewhere....

Not to disagree with kjc, lifters and the valve train can make plenty of noises. (that can get better when it warms up) Some guys have posted some success substituting one quart Marvel Misery oil at an oil change. I guess it has solvents that can help dissolve deposits in the lifters.

 

Maybe I have a little piston slap then, but it sounds like my rods aren't worn or too warn down then because my noises go away. I'll have to pick up some of the mystery oil, whether it fixes problems or quiets them down I'll take either.
__________________________________________________ _____________

I might do that, I got my oil changed at a local place and I asked what kind of filter they used and it was just some generic one, I made sure it wasn't fram. I'll get my own next time.

__________________________________________________ ______________

Thanks for the help guys, it really calmed my nerves as far as engine issues go.