People keep wording it that way but it’s not all units being shipped to dealers. It’s all affected 2021s. That may still just be units with
motors built by April. Again, I’m not defending GM for how they’ve handled this with customers - they should bend over backwards to satisfy a buyer dealing with an engine problem.
I think this is right. GM had a bunch of vehicles that were "mostly" assembled that were waiting for back ordered parts to be completed. I think the "affected vehicles" are ones built with engines assembled in the then "bad lifter window" but sat undelivered while they waited for the back ordered parts.
The engines in question had two component issues. Lifters that had an improperly heat treated lock pin spring that when it broke, caused the lifter to fail. It also covers another completely different issue of valve springs that were improperly heat treated and were also subject to failure. At least, that is what my guys locally are telling me.
It is kind of stunning that someone at GM didn't say, "hey, with all those trucks we have stored waiting for final parts assembly, why don't we cycle them through and replace the suspect lifters and valve springs, while we are waiting for the chips to finish the bells and whistle components?" Ah no, let's just wait and when we finally do get them completed and shipped to the dealer, we will have them do it at double the price...