BotaLoda remember, if those pins were built larger in dia. to hold more pressure, and you continued using it as you were....what would have broken then?
When any machine/tool is used beyond it's capacity something gives up. Your situation is very, very rare in Kubota tractors. You were just misguided in the use of your tractor. Take the new knowledge and use it accordingly, you'll be fine from now on!
And if you're not sure about something, just ask before attempting. Someone will help.
D2Cat, with the question of what else would break if the pins didn't, it made me think of my 55 chevy hot rod. I put a newer "12 bolt" rear/transaxle in it to handle the power/torque of the motor. Trying to compare it to the locking rear isn't really that great of a comparison since it doesn't have a differential lock, BUT... the gears in it are strong. The weakest link right now is the axles. I first had some really crappy ones a shop stuck me with and I twisted an axle from taking off at the drag races. Never would have known it if I hadn't been taking it apart to change gear ratio. Eventually the axle could have twisted enough to break, it happens. Luckily the repair if I was paying a shop, would be about $500 with parts on the high side. (I don't have C-clips if you know what they are). So anyway, if the axle were the weak link on the tractor, it also would be a repair of no more than half of what this warranty work would have cost me. That's if the info to pull an axle on the BX is correct. The unit would not have to be split in half, much less labor and less parts. Actually I just looked somewhere else and it looks even easier than I thought to replace an axle. $235 for the axle and some more for a seal. Less than an hour for a pro and 2 hours for me, instead of 12 hours (which the mechanic must have been good to do that in 12 hours!).
Sorry this go so so long. To make a long story short, put the cheap parts where they are easy to replace!
Trust me, that diff lock will be babied from now on. If out of warranty that job would probably take me a good 40 hours instead of 12.