Can opener type grinding sound coming from underneath truck

[ATVGMC08]

2008 GMC serria 5.3 4X4 AUTO 76,000 MILES AUTOMATIC TRANS
At first when it just started to happen I thought it was related to the air conditioning Put on the further examination I don't think it has anything to do with the air When I shut the engine off you can hear the grinding winding down Definitely is relative to the engines rpm Any help would be greatly appreciated Thank you very much and have a wonderful day

 

[GMC Customer Service]

2008 GMC serria 5.3 4X4 AUTO 76,000 MILES AUTOMATIC TRANS
At first when it just started to happen I thought it was related to the air conditioning Put on the further examination I don't think it has anything to do with the air When I shut the engine off you can hear the grinding winding down Definitely is relative to the engines rpm Any help would be greatly appreciated Thank you very much and have a wonderful day

Hello ATVGMC08,

I am sorry to hear that you are experiencing this grinding noise coming from underneath your Sierra. I see that you are looking for any suggestions from the community here, but if you were interested in taking your vehicle into the dealership regarding this concern. I would be more than happy to assist you in working with them in regards to this concern. Please feel free to private message me if you would like to further discuss this concern. Thank you very much for your time.

Gregory W.
GMC Customer Care

 

[ATVGMC08]

It seems to be if i rev enging in nutral or park the growl speeds up and slows with the revs but i put it into drive or reverse it goes away