Grinding/Buzzing noise under truck?

[docholiday17]

Been trying to find out what this noise is for the past 2 weeks or so. So far I already replaced the transfer case motor and flushed the power steering fluid to no avail.

 

Noise just started happening completely out of the blue on my 2000 Silverado 1500 5.3 4x4. Only does it when the truck is on. Doesn't matter if I'm in park, reverse, drive, neutral, actually driving, etc. It's most noticeable when stopped though. Upon a closer listen the other day, it sounds like it's closer to the transmission area, like near the pan. Closer there than the transfer case. There's no codes or dummy lights on. Sometimes the sound goes away for awhile. But it's generally pretty consistent. 

 

 

 

 

[davester]

I would suggest using a mechanics stethoscope to narrow down where exactly the sound is coming from.