Not exactly what I hear, but the sound Transient mentions, a hard object dropping on plastic rings a bell....and follows RPM. Where is it coming from, top... bottom... trans area? I have a low frequency noise that started in my 23' - 5.3 that I hear in the cab, and under the truck, not so much under the hood, but a little in the wheel well. It follows the revs of the engine, like a small engine pop pop pop exhaust like sound more so than a knock or ping...then the tires drown it out above 20mph. Dealer replaced the TC and front cover...Noise was gone when I picked it up, then by the time I got home, it was making the same sound again. The service order noted the oil pump drive gear as the issue.. replaced with torque converter...see GM service bulletin 22-NA-232. Now I'm on week 5 without my truck, I love this truck, and that 10 speed shifted so much better than the 6 speed in my 21 TRLBSS, That's one of the reasons I traded it in. So I wonder if the pump gear was the cause, or affected by something else. Take it in and at least file a case number for record. If they find and fix it great, if not you have a history. This is the last update I have from yesterday, word for word......."we think the cause is lower end engine problems, which our trans tech says could have contributed to the TC and hypoid gear from last repair. We have started at TAC case to find out what GM would like us to do in the break down of the lower end of the engine...................11,000 miles!!!! Found GM Service Bulletin 23-NA170. Can't wait to see what happens next the suspense is killing me he says with intrepid voice......Trying to stay positive...........Hope your issue is simpler, but if it's a new truck, get it it in and the ball rolling, Note I have a Custom, with no Active Fuel Management, but guessing the same lifters as with AFM, ...I'll take a 6.2 swap!!