Art, it sounds like you agreed with most everything I said.
This part though I will try and explain better. As I said this was what one owner told me and from what I have read it makes some sense. The 4wd didn't have to be backed up or turned to turn it on or off. What he said was if you were on hard ground and backed up or on pavement going either direction it could break the drive shaft off going to the front axle. This was on a IH 1466. The reasons were on any 4wd I know of the front tires turn at a higher ground speed than the rears. With a modern 4wd the weakest link is the tires and they flex enough or slip enough to allow this. The reasons explained to me are that the drive shaft spins at a much higher speed than needed till the hubs. At this point the planetary changes this from a high speed low torque to a lower speed higher torque. On the early IH that didn't have this set up the drive shaft wasn't able to transmit the torque. When the tractor backed up the front tires seemed to "bite" in harder and couldn't slip, or on pavement couldn't slip. It may also have been due to the shaft went down from the top of the trans down to the axle. Kind of a funny angle. I also saw a few of the drive shafts in his shop that had been twisted.
As I said that was how it was explained to me. Maybe someone can explain better or maybe I'm incorrect. Seems to make sense since most every 4wd farm tractor, backhoe, loader etc today uses a planetary axle set up.
To your point about tires, I can also see that doing the same thing. I remember reading about a mining operation that saved money on drive train repairs by keeping the tires on the loaders within a certain percentage of size. They had one figure they used to keep between tires on the same axle and another from end to end. If they replaced a tire on the machine, if they didn't have a used tire close in size, they went with 4 new tires to keep them within that spec. It seems like that more than doubled drive train life.
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