Engine knock

I heard this sound clip from another thread (thank you ChipsXJ).
http://s2.photobucket.com/albums/y16/ChipsXJ/?action=view&current=000_1316.flv
I have a 91 4.0, 150,000 miles AW4. Oil pressure seems fine 60 at start up after warm up 5 min or so it's about 18 or 20. I use 10w30 oil.

It sounds identical to mine. It has gotten gradually louder over the past 8 months or so. At first the knock almost went away after the engine warmed up. Now it sounds like the clip at start up and gets a little quieter after warm up. It was quieter in drive, foot on brake and stepping on gas. Over past couple of months if I do this, it is louder then before. It is quieter in drive then in park.

I am kind of just waiting for it to blow up. I know the easiest thing to do would be to take it to a mechanic and find out whats wrong. I am just afraid to take it to someone I don't know and they tell me it needs a new engine if it doesn't. What could be some easy things I can do to check for myself?

Look for metal in oil, always take off the inspection cover on the bellhousing and make sure you don't have loose tc bolts, that is common on auto cherokees, if u have low oil pressure that is sometimes a sign of bad bearings, you could take a stethescope and try to pin point the area that it is coming from, I have also read (while the engine is off) pull a plug, start it up, if it gets louder thats your prb cylinders bearings to detect if it is a rod bearing, then shut it off and reattach the plug wire, do not do this with the engine running, you could get shocked, how many miles are on this engine?....does it get regular maintanence, could also be piston slap which is pretty common and harmless, does the noise increase with rpms or under load?

Get a mechanics stethescope
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=41966
and find out exactly where it's coming from.
A lot of people seem to like broom handles, but for <$10 :dunno:

Using a stethescope is it easy to find out where a noise is coming from?