I have to admit that I am not very mechanically inclined. I do very little work on my own vehicles (starters, alternators and brakes are about it). So, I am baffled as to the cause of this. I don't think the transmission broke if you are talking about the guts of the thing. But I also didn't spend a lot of time checking the tractor out. I knew it was something that I could fix and I figured the less I touch it the better. I was also pretty much devastated and trying to figure out how I was going to get all the hydraulic fluid off of my new drive and new garage floor. What a mess! Although the 160 pounds of oil dry did a pretty good job. I do have a stain on the drive but I am hoping it fades over time.
I did speak to the service man at the dealer I used. He said they did not find any missing pins, but will put the deck back on to make sure everything works okay before I get the tractor back. It may be my lack of mechanical knowledge, but I am amazed that the case broke unless there was a defect in the casting, even if my deck was out of adjustment, which seems to be the theory. I would have thought that there would be some sort of bypass or limit on the hydraulics or you could be breaking things all the time. As I said, I am no mechanic and this is my first tractor, so I could be way off base. My biggest concern is that this doesn't happen again.
Overall, I love the tractor and am less pleased with the dealer because of other experiences I have had since I bought the tractor. I took a month longer than I was told to have the tractor delivered when I purchased it because they had to wait on a loader, then had the wrong brackets for the mower. I was told they would show me how to take the loader on and off, work the mower etc... on delivery but the delivery man had no clue how to operate the tractor and couldn't show me anything. The mid PTO did not when I first got the tractor because a wire was unplugged. It was clear to me that they had not gone over the tractor before they delivered. When I had the 50 hour service done, I had to take it back to the dealer a second time to have the transmission fluid changed because the service man didn't realize it was a hydro. He also had to replace an O-ring under the seat and fix the tilt steering wheel on the 2nd visit, which I don't consider to be the fault of the dealer or JD, but just a defect or faulty part, which can happen with anything. I also referred a co-worker to them for a 300 series mower, right after I bought mine and they did not have a good experience. Individually, none of these things would bother me, but collectively, I have been irritated at times. I might use this dealer again in the future because I think some of the problems I have experienced are just flukes and once I get the tractor back, I will be reminded of how much I like it and why I chose the 4310 over other makes that I looked at.
