Again, I appreciate everyone's helpful comments. Elcamino...that is exactly what happened to me...mine failed at 20k miles and they only replaced one side and I'm not even sure if they replaced them with non defective parts. I have heard that if your GM vehicle was made between 9/20 and 3/21 then you may have defective lifters which are more prone to premature failure. Mine unfortunately was made in 12/20. GM will issue an extended 100k warranty but you have to have 2 reported failures.