Mine never happened during reverse, or would only happen when it was downshifting slowing down, it would make the noise then it would feel like it would “re-engage” into gear. Atleast that’s what it sounded like.
It’s a 2015 Silverado, it was the transfer case, I put in a different one because it was cheaper for me than to rebuild, but I would assume it was the chain also as mentioned above.
Yes, I ended up finding a cheap transfer case with less miles than my truck. So I’m not sure what was happening in the transfer case I haven’t had time to pop it open to investigate.