What are they doing with cores. Son in law had a dodge ram with close to 300 thousand on it. Rear end went out so he went to a salvage yard and bought one. The yard wanted his old one exchange. Got the one from the yard installed and it was in worse shape than his old one. Mechanic that did exchange told him, let me just rebuild this one for you. He didn't want to try a salvage yard again. Went back to yard to take his original rear end and get his deposit money. Told them rear end they sold him wasn't any good. Yard said just bring it back and we will return your money. In his case it was cost prohibitive to change it out twice, better to have it rebuilt. In hindsight it would have been much better to have the original rebuilt.