The only issue I have had with my axle, is my steering knuckles kept coming loose (both sides). I replaced every bolt and washer only to have them loosen again. I replaced washers with NordLock washers and my problem is behind me. Gone, permanently fixed. I now have one U-joint, although it is laced, that the bolt is loose, so I need to disassemble mine, tighten it and quite possibly, while in there, I will replace the U-Joint.
Now, having said that; let me state that in all the years I have been working this issue: looking for Schindler axle parts: I have not found one part number posted anywhere, on any forum. (I did get a personal email from a guy with part #, but they were not OEM, only the number the warehouse he got them from databased them with. While there have been numerous comments, no actual part number help has been provided. Please be the first to post the part numbers of the parts you find, and replace, if indeed it turns out your axle is a $chindler. There are 5-10 of these axles in the US, fitting Ford 3000-8000 tractors. You'll help out all these fellas.