2016 - Consistent Noise (whirring ?) while in motion - RESOLVED - See my latest post for required repair and parts

[crhoades68]

I have an issue and have searched the troubleshooting section but haven't found a thread that really matched my issue.  

 

I recently purchased a 2016 GMC Sierra 2500HD 4x4 (Regular Cab w/ 8' bed) with 55k miles.  When I test drove it all the area roads were either rough or under construction so it was hard to determine much via the test drive.  The truck looks in great shape and had good service records including a clean Car Fax.  

 

Once I had driven on familiar roads I noticed a noise that I'm now trying to diagnose and fix.  I'm not sure how to describe it but I only hear it when driving (at all speeds).  I hear whether or not I'm towing.  The noise doesn't get louder with speed and I don't hear it at idle.  The dealer had installed new tires (General Grabber) on the existing base 18" wheels.  The ride was rougher than I thought it should be and I knew the torsion bars had been cranked.  I think it is back to or close to the original ride height and it improved the ride but I still hear the noise.  I know that it's not wind related because other people can hear it but it's not so loud that everyone turns and looks at the truck as it passes.  I've looked at everything I can think of but don't find an external source.

 

Any thoughts or ideas would greatly be appreciated.

Edited July 27, 2021 by crhoades68
Update status of issue

[crhoades68]

Here is the follow up to my original post which was basically that I was hearing a constant noise from the rear end while the truck was in motion.

 

I decided to take it to a dealership.  Following is the technician's note.  "Test drove with chassis ears, rear differential noisy.  Disassembled rear differential.  Lots of metal on magnet, multiple bearings worn.  Replaced multiple bearings, pinion, carrier bearing, and set up backlash and all bearings preload, cleared metal from housing.  Test drove vehicle."  According to the service rep, this would have been around $2,800 but was covered under warranty.  Below is the list of parts replaced.

 

Qty     FP Number     Description

2         9436881         Bearing Y 5.855

1          9414917         Bearing Y 5.447

1          23243839     Bearing Y 5.526

2          20920620     Gasket Y 5.811

1           26064030     Seal Y 5.469

3          88900401      Lubricant N 8.800

1           26067159      Gasket Y 5.399

1           26008741      Spacer Y 5.476

 

No prices provided since it was a warranty repair but was told the parts would have been around $1,800.  The repair took 7.2 hours.