There was some pictures floating around here that showed the differences between the axles. I don't know if anyone remembers where they are or if someone saved them or not.
JD 4520, Toolcat 5610, Bobcat S300, Case-IH 125 Pro, Case-IH 245, IH 1086, IH 806
rmonio
I think the problem was on the very early years. I can't quite remember but the problem may just be on the 1999 models. The problem was corrected by the time of your 2001 4600.