I have a 2020 sierra crew cab with 5.3, 10 spd trans and having low speed vibration 28-10 mph (deceleration or acceleration). I took vehicle to dealership on Monday. Two days later dealership called and stated all the test they performed (DFM, Trans mount ect..) was working as design and nothing could be found to cause issue. During this call I stated to service manager what was I suppose to do just live with this issue. I also stated that i was on GM truck forums and there where numerous identical issues, do I need to have a GM-Tech reach out to them? Service manager said let me talk to shop foreman/supervisor and see if there is anything he can do. Next day service manager was having another Pico scope test done to try and find issue. UPDATE; Shop foreman/supervisor called GM-Tech and they requested another Pico Scope be performed and to send them the results. Currently waiting on GM-Tech for guidance from Pico Scope results, should hear back from GM next week. I requested a loaner vehicle and dealership stated i could come get my truck and that it was safe to drive until they get the guidance from GM next week. Will update when GM gives guidance.