Strange exhaust-like vibration noise traced by dealer to transfer case.?.

[chrisbusnut]

So I have had this strange vibration/buzzing like noise coming from what sounds like the rear underside of the vehicle. It happens when accelerating from low speeds as the RPMs get to about 2200, usually shifting from 2nd to 3rd gear. The noise sounds like part of the exhaust vibrating on a heat shield, or something like that. After 3 trips to the dealer, during which I was able to duplicate the noise for the service manager (he acknowledged the noise), it was supposedly traced to the transfer case. I had been driving in Auto mode, and was told that when they switched it to 2WD mode, that the noise immediately went away.

They told me that I should always drive in 2WD mode, unless I'm in a situation where I may need 4WD. I'll admit, the noise is either greatly reduced or gone altogether in 2WD mode, but I'm having trouble buying that I shouldn't be driving in Auto mode. I also have a 2020 Sierra HD Duramax that I exclusively drive in Auto mode, and I've never heard this type of noise from that vehicle or any other current body style Tahoe, Yukon or Suburban that I've driven.

Has anyone else experienced a noise like this, and is the dealer jerking my chain when they tell me to only drive in 2WD? It sounds to me like they don't want to address the real issue.

 

[TXNJ]

So I have had this strange vibration/buzzing like noise coming from what sounds like the rear underside of the vehicle. It happens when accelerating from low speeds as the RPMs get to about 2200, usually shifting from 2nd to 3rd gear. The noise sounds like part of the exhaust vibrating on a heat shield, or something like that. After 3 trips to the dealer, during which I was able to duplicate the noise for the service manager (he acknowledged the noise), it was supposedly traced to the transfer case. I had been driving in Auto mode, and was told that when they switched it to 2WD mode, that the noise immediately went away.

They told me that I should always drive in 2WD mode, unless I'm in a situation where I may need 4WD. I'll admit, the noise is either greatly reduced or gone altogether in 2WD mode, but I'm having trouble buying that I shouldn't be driving in Auto mode. I also have a 2020 Sierra HD Duramax that I exclusively drive in Auto mode, and I've never heard this type of noise from that vehicle or any other current body style Tahoe, Yukon or Suburban that I've driven.

Has anyone else experienced a noise like this, and is the dealer jerking my chain when they tell me to only drive in 2WD? It sounds to me like they don't want to address the real issue.

please update this as time goes on because I just noticed some kind of rattling/vibration type sound that I notice primarily at fairly low speeds over slightly bumpy roads. It literally sounds like a loose exhaust somewhere around the middle-rear of the vehicle. I drive in "normal" mode, which is 2wd.

 

[Stbentoak]

Mine is going in next Monday for TSB fix for missing or not secure Heat Shield retainer nuts. the # is PIT5926. I have a rpm related rattle/hum while sitting at lights with foot on brake. I bet it is a heat shield and I hope this TSB fixes it.

 

[Pertzbro]

You should be in 2wd mode unless in snow or offroading or "racing". Driving around in auto will just hurt your gas mileage and add additional wear and tear.

 

[B-train]

What @Pertzbro said. No need for auto all the time. You are making the front axle and transfer case stay in 'ready ' mode which just adds more wear and tear to the system. Use if for iffy weather or off road conditions.

 

[GoNoGo]

Drove a '23 Tahoe 6.2 4wd for about 45 days earlier this year that it too had a similar whining noise from rear undercarriage esp noticeable between 40 to 55 miles per hour, very aggravating to me since I don't listen to radio.

Decided to trade it in on '23 Suburban 4wd with diesel powertrain, lost a few bucks but now extremely happy.