Most locales with sizeable population centers have auto repair specialist shops that do this kind of work every day. Repairing drive line stuff – drive shafts, u-joints, differentials, transfer cases, axels, axel bearings — that’s what they do, that’s their business model. So one idea is just pack up the unit and take it to one of those shops. It does’t matter that the OP lost the reference marks. They deal with that problem all the time. They’ll know how to put it back together, and how to diagnose it. I’ve never had to use one, but I expect they appear in the yellow pages.