2002 Escalade 6.0 Stock Exhaust Resonance--buzzing, Moaning Between 2,

[RLGDiesel]

Hello...I own a 2002 Cadillac Escalade AWD 6.0 with 80,000 miles. It's been a great truck but recently developed an odd sound in the exhaust when accelerating from a stop/coast/roll only between 2,500 and 3,000 RPM (in any gear). It seems to be a louder and rougher sounding buzzing, moaning, or humming sound. Could this be a baffle or cat failing...does anyone have a similar experience?

 

P.S. It doesn't really sound like a heat shield to me since it happens erratically (but consistently in the same RPM range) and tapping on the exhaust pipe does not produce the "rattle."

 

UPDATE: I took the car to a GM dealership today and they examined the exhaust system with me. When the tech hit a portion of the pipe behind the cats, the metal ring above the O2 sensor vibrated and rattled throughout the whole pipe. However, after replacing the O2 sensor, the buzzing and moaning persisted at the same RPM range. I mentioned the heat shield and clamps, but the tech could not duplicate the sound when tapping the muffler with a rubber mallet.

 

Thanks in advance!

[superjim]

Probably a stupid question...but have you tried to reproduce the sound with the truck stopped and just increasing the RPM to the specified range?

[RLGDiesel]

I normally cannot reproduce the sound by revving...it is most pronounced under load. Thanks for the reply, though.