I had the exact problem with one of my previous Tahoes. The dealer owner is a friend of mine and he told his guys to Road force balance the tires. Issue solved. Each tire on your RST weighs about 40-42 pounds, plus the weight of the rim (at least another 20 pounds?). As good as the current tire and wheel manufacturing processes are today, there are tolerances and therefore are not absolutely perfect. A traditional regular balance job is usually good enough for everyday driving vs. competition use. The bigger the tire diameter and lower (stiffer) the sidewall, the worse the ride and the more prone the combination is to magnify the out of balance condition when you get up to highway speeds. Usually when tires are mounted most "technicians" just randomly install it on the rim without any regard to the highest point on the rim (some color dot or marking) and the lightest (yellow dot) and flattest points (red dot) on the tire. A GOOD installer will identify and align the tire appropriately on the rim. Road force balancing introduces a roller that simulates the force working against the tire and identifies the radial and lateral forces when in use and ultimately gives a more exact measurement of how much weight and where exactly it needs to be placed. Press your dealer to road force balance all tires. If you truly have a vibration after that rather than just a stiff ride that just accurately transmits the imperfections on the road, you may then have other problems. (However I would doubt that.)Bought my RST in July 2023, after having a 2023 Tahoe LT for almost a year, loved my LT but wanted some of the things the RST had that my LT didn't. Now I am wishing I hadn't. I traveled to another state to purchase my new RST, noticed almost right away that it rode rough, seemed like maybe the tires were not balanced. I took it to Chevy after 500 miles, they checked everything & only performed an alignment & sent me home, Tahoe was still doing the same thing, they told me I needed to drive it to 1500 miles before they could do anything else, so I did. Took it back in, they called & told me it had 2 bad injectors, so both injectors replaced, they also replaced the driver side valve cover because oil was leaking into cylinder 5, which they found when inspected, they also replaced all 4 tires, saying they all had flat spots. Just got it Friday from these repairs but again, it still has the same vibration, as if the tires aren't balanced, that's the best way I know how to describe it.
Anyone know what they are missing? I feel like I am going crazy with this new RST & wish I had not made the change because my other 2023 drove so smooth.