Noise from Oil Pan

I have a 94 Jeep Cherokee inline 6. In the last year I started noticing a cladder coming from the engine. I thought it was the nature of the beast, being an inline 6. Later I noticed a dent in the exuaght pipe right under the headers so I contibuted the clatter to the restriction in the exuaghst and still wasn't too concerned. Until today when I took a stethascope to the clatter and found it coming from the large area of the oil pan. The cladder gets quicker when I accelerate. I run a high octane gas and 10w30. I had an emissions test done today to get my inspection and it passed with flying colors. Does anyone know what the problem might be? The Haynes mannual talked of a piston rod lashing and suggested removing one spark plug boot at time and starting the engine. I did this and the clatter remained. Help!!

sounds like you will have to pull the oil pan and check bearing clearances. this is most commonly a problem of running the oil low or not changing it often enogh. that is not always the case, but it does sound like you have a very tolerant bearing. I have a light knock in the bottom end of my xj and have had several suggestions of a loose bearing cap

The "dent" in the exhaust pipe is supposed to be there. Check the noise at the flexplate cover. If the noise is louder there you might have loose torque converter to flexplate bolts.