bottom end noise

[00Xplorer]

About a year ago I got this chattering noise coming from the bottomend towards the back of the engine oil pan/ bellhouse area. The noise just appeard one day after a oil change. I can hear the noise all the time cold or hot. Noise is loudest in park or neutral and noise does go slightly with rpms untill about 2000rpm then I can't hear it. Car is a 2000 explorer xls v6 ohv with 143k miles. And noise started around 130k miles. Also noise has stayed the same and it is not any heat shields or cats. Any help will b great.

 

[00Xplorer]

Any ideas

 

[drdoom]

I don't know, but when I get back to our shop later this week, I have to try to find a similar racket on my SOHC. I was thinking it is cats or shields, but now I am thinking alternator. I did check the cats with an infrared, for what that's worth, and they seemed OK. The noise seems to reflect around a bit, makes it hard for me to find. I am going to pull the serpentine.