Just wanted to say thanks for starting this thread. I have the exact same tractor and loader, and the exact same failure of the loader mounts. My situation may be even worse because I've added a much heavier 4-in-1 bucket to the setup. I bought the tractor from a fellow that was using it to clear land in the Santa Cruz mountains south of the San Francisco Bay Area, and from the looks of the bucket and loader arms, this thing really took a beating. Both mounts were broken and weld repaired when I bought it, and both have since cracked again. The first time this happened I ground out the cracks and welded them with MIG and E70S filler, but the cracks came back in the heat affected zone of the weld. Gouged 'em out again and this time preheated to about 400F and let them cool by themselves. That worked for another couple hundred hours until one of the mounts started to crack again. I was in the middle of a job and kept using it until it broke all the way across at exactly the same place as the OP, right through the casting and the side plates that had been added in the original repair. This time I took the mount all the way off the tractor, put a bevel joint on the broken pieces, and again used preheat while welding them back together. I also added a fair amount of filler metal to the webs on the back side of the casting to help reinforce the crack zone. So far I've seen no additional cracking on that side, but now the other side has about an inch of crack that is slowly growing.
I'm going to make a copy of this thread and take some pictures of my mounts and go have a talk with my Kubota dealer. Since the tractor is 8 years old with 1800 hours on it (only a third of them mine) I'm not expecting much. But if Kubota is aware of the problem and they've revised the mounts, it will sure save me a lot of welding and grinding if they're willing to replace them at no cost to me.
The property here is pretty steep and I've moved a lot (if you can call 200 cu. yds. a lot) of fill dirt while running sideways to the slope. I've noticed, especially when I hit a bump with a full bucket, that the upper arms of the mounts flex at least a quarter inch sideways, and that's probably what is causing the cracks to initiate. Those same side loads keep loosening the bolts securing the inner covers on the front 4WD hubs, and what a mess that makes. First time it happened I didn't catch it until the cover broke, sending the wheel and axel out in front of the tractor! My take away from this is that these little tractors are great for landscaping on soft level ground, but here in California's Sierra foot hills where the terrain is steep and full of rocks, they just don't hold up. My neighbor likes to say that Kubotas are fine for maintaining things, but you need a real backhoe to build things.
BTW kcender, when I saw the photos of you moving those dirt mountains, the first thing I thought of was that song about the ant and the rubber tree plant
