Vibration and rattling in 2017 Tahoe Premier

[mburbank]

Hi!  I'm hoping someone can help me with some annoying issues with my 2017 Tahoe Premier with 22 inch wheels.  I'm not technical at all with cars, but the ride has deteriorated significantly to the point that there is a lot of rattling in the rear and bumps on urban streets are incredibly annoying.  I took the car to the dealership where I bought it, and they suggested I replace the tires, have them balanced and aligned.  So I did that (with Michelins).  When that didn't fix the issues, they "opened a TAC case" and "found that the rear shocks were locked up."  So they replaced them (under warranty).  While this was going on, I had a 2019 Tahoe loaner and it rode like a different car.  When I picked up my car, I drove around the dealership (pretty new roads) and it felt fine.  Got a few miles away and crossed a train track and it felt and sounded like the car was going to fall apart again.  Got back to my part of town with worse streets, and I'm still hearing rattles and feeling every bump.  At this point, I want to dump this (very expensive) car.  I have about 1300 miles left under warranty, and I'd love to get it fixed so we can get some more life out of it or I can sell it privately.  Can anyone suggest next steps?  Should I record the sounds while my husband drives?  Contact GM directly?  Does anyone know the right words I should use to describe what's going on?  Could it be the axle since the shocks were already replaced?  Should the front shocks be looked at?  Thanks for any suggestions! 

[The Zip]

Could be something simple like a broken or loose bracket, I"m guessing the dealership checked for this when replacing the rear shocks?  Recording the sound while your husband drives is not a bad idea for reference.  At the very least I would schedule another appointment.  Before going in, drive on roads around the dealership which causes the rattling in the rear.  Pick up the service writer and take him for a drive on the roads you know causes the rattle.  Then ask him the next steps since there is only 1300 miles left under warranty. 

[Mandalorian]

Look up the lemon law process in your state, to be safe. Otherwise, since it's still under warranty, try to get them to replace as many suspension components as possible.

[The Zip]

3 hours ago, mburbank said:

 ... a lot of rattling in the rear ...

Take a ride in the third row so you can be a bit more confident that the rattling in the rear is inside or outside and advise the service writer what you believe.  But tell them to look at everything from the second row back, inside and out, roof to chassis.