I have a 2008 Silverado 1500, 2WD, 5.3L, 121,000 miles. It started making a loud grinding noise when I turn it off. I tried having a friend turn if off while I was watching but I couldn't see anything obvious. It sounds like its coming from the front of the motor somewhere but I don't know where. Does anyone know what could possibly be making this noise? It doesn't make any abnormal noise when I'm starting it.

 

?dont know about a grinding noise, i know just recently on mine i noticed a "farting" type sound when i turn mine off, kinda like a air puff noise. i took it to the chevy house even tho my engine light never came on just to check on it, the rep told me that the fuel flex(if im not mistaken) usually do that.:shrugs:

 

Have them check your Motor Mounts. The one on the Driver side goes bad.