The Jacobsen is still not completely diagnosed, but I'm thinking the input shaft of the Eaton is supposed to spin, not have a 1" wobble to it. It has an inch side to side, up and down, all over the place play, but won't spin either direction.
Something went to poo-poo inside there! Never had one apart, not even taken one loose from the axle. If you did replace the Eaton, I imagine a good flushing of the axle would be a necessity.