when my tractor got delivered to my house and the sales guy was walking me through it all and showing me examples, I specifically asked if it was filled as I heard there have been issues lately (2021 is when I got it) regarding front axles on the smaller series. He told me they have had to top off the front axles on most of their deliveries, and told me he also did the same to the l2501 sitting in my driveway. I should have checked it that day but was a bit nervous to start taking out bolts on a brand new machine when I had no experience operating anything bigger than a ride on mower with a 42 inch deck. I did check the level at my 50 hour service since I already had the wrenches out and it is pretty much level or just a hair below the check bolt housing. I just checked again two days ago after reading this post, as I have put 25 hours on it all in 4wd since mid December and figured it would be good to look. Thankfully Once again it was about a hair lower or pretty much level with the housing. I also didn’t notice the nasty smell you get when a diff or gear oil burns. I’m probably going to end up changing it earlier than recommended just to ensure longevity as I’m not putting tons of hours on it.
IMO it’s not your responsibility to crack that thing open until the hour meter says 400 or whatever the interval your manual says. Unfortunately the QC and PDIs suck in the US for vehicles and manufacturing it seems for some reason so we all probably need to start to verify everything. Just had an incident with my snowblower with the shaft not being tightened properly at the land pride factory.
When you go to drain the axle/diff, I would recommend putting a magnet in the drain pan to see what comes out. I would think if it’s not full of sparkles or a lot of metal shards you should be good. Honestly it’s probably worth it to call the dealer or Kubota customer service even if your past warranty. If it’s a good dealer I’d imagine they would make it right.