The lift arm shaft thru the differential seals leak and I heard that replacing seals won't fix it, that there is a kit that is needed to repair it. Has anyone run into this and know for sure? This seems like a poor design to me.
I have had 40 and 50 series JD tractors that developed leaks on the seals that you are refering to. I have replaced the seals and usually get a couple of years out of the new ones. The times that I didn't have luck required me to replace the shaft because it had become deformed. There were two different types of seals available, one was a poly seal though I am not sure, but one always worked better than the other. Relatively simple repair after removing all the fluid.