When my sister/BILs coach blew a head gasket and warped the head, they were just out of the 5 year (I think only a few months, less than six if I recall), and they talked with main and local Cummins, and was told that the local Cummins has the authority to make decisions on out of warranty. In this case, they concluded that it was likely an over torqued or faulty bolt that broke. They didn't fully cover it, but I believe charged them about the cost. Something like going from a $10k bill to $5k or something like that.
In their favor, was the fact that they could tell in the computer that as soon as they got the low coolant/shutdown engine, they did so immediately (were in the process of pulling in or out of a state park, if I recall correctly). So, it was clear they didn't drive it despite low coolant or other things where their actions would have made it worse. It was pure manufacturing failure.
I'm not sure how far out of warranty you are, but if it's close, and you have from the previous owner records showing it was properly maintained, it's definitely worth trying every avenue you have, including seeing if Cummins has a customer advocacy department.