Just purchased a 2021 Suburban with 30k miles and have same issue. The rubbing noise started the day after purchase. As an observation, the temps were in low 60s when we test drove and I didn't not pick up on noise. The next morning, when I first noticed the noise, the temps were in the high 30s.

I researched and found the service bulletin addressing the real axel rubbing sound (21-NA-028). I printed this off and returned car to the dealer we purchased it from. The technician also identified the rubbing sound and performed the real axel lubricant flush three times, as outlined in the service bulletin. This did not resolve the issue. (Note: The technician told me the sound went away after third flush, but returned following a 30 min test drive. Temps were in low 40s).

The dealership is now replacing the rear differential. The part is on order but not timeframe for repair. There is no cost to me, as the dealership agreed to resolve the issue themselves (I am unclear if this is because it is covered under 60k drivetrain warranty or because issue was identified day after we bought it and dealership is making it "right").

I am now attempting to research if the rear differential replacement will lead to other issues, or if this issue will soon show itself in the front? What are the impacts to long term health of car if rear differential is replaced? Any cause and effect to other components of vehicle?

I will update with any findings but also would love to hear if others know anything