Hi Ranger 1,
I think that you being very astute type bloke, your initial observations between new and old pump bearing assemblies- you would have spotted the groove milled in the old bearing assembly. From an old head/memory there were not any, either lineal grooves or radial ones. Correct me if I am wrong. They were originally ferrous bronze type sleave bearing, possibly the bearing content material content has metalurgically changed with the upgrade coc up. There is nothing like spinning tales to protect from warranty potential costs.