jeep engine knocking?

my 4.0 does the samething when i 1st start it, it has a moderate knock but after a minute of idle it settles down. it has 177500 miles on it and i upgraded to a high mileage 10w 40. oil though may not be the issue. you might have a bad lifter that is late priming up after startup or rocker arms are loose and need adjustment. might want to check them. you say you have a hard knock. jeeps are bad at cracking flexplates which is located at the end of crankshaft of engine where the trans connects to. the engine may not be knocking but the flexplate maybe broken and that knock is coming from flexplate. that happened to me before had to drop the trans take the flexplate off and weld it back together then the knock went away.

You engine must have a lot of miles on it (like 150k or more). Next time you change your oil try going with a thicker oil next time. From a 5w-30 to a 10w-30 or 10w-40. See if that helps with the knocking when it first starts up.

you may desire to easily replace the 4 banger with a quickly six, because of the fact which you may get a used one w/ tranny for much less costly and continuously rebuilding the 4 cylndr would be greater costly in the long-term

Check your oil.