Knocking sound, worn rod?

Got a 95 4.0. When you rev it up it will begin to knock around 2000 rpm. Took off the valve cover and it sounds like it's coming from where the rod connects to the piston. Anybody had a problem like this before?

I've probably put 500 miles on it since it started to do this. Any input is appreciated.

Sounds like a wrist pin. Mine has had a piston slap for 80,000 miles and it still runs... Get under it and listen to the rod/main bearings, if you don't hear any horrific noises underneath, I wouldn't really worry about it.

That's what we figured. Couldn't think of it before, but you hit it right on the money, wrist pin. It's the middle of sledding season and I put 400+ miles almost every weekend on the XJ so it looks like I'll just run her til I can rebuild it during spring break. Hopefully she makes it.
Thanks nekocopter