If you are asking about what is covered and for how long, I would try the MFG web site. May either find it there, or a phone number to call. If you are asking about warranty on repairs done under warranty, I would guess the same thing.
After 5 splits in 2 years, the regional rep and I would be on close terms. Call him/her up and calmly and politely go over the time line of what has been done to you tractor and without any passion or aggression, tell them that it needs to be fixed so it stays fixed. Also that you have begun to loose faith in the manufacturor and the dealer's ability to repair the tractor. Should you feel like you are getting the run around at that level, ask the regional rep for names of higher ups and contact them. I would also send informational letters to very high ups. Again, the web site can aid you in getting the name of the directors of manufacturing and of quality. Writting them polite letters explaining that you have been patiently working on getting your tractor fixed and would appreciate their looking into why it has not and is apparently not being fixed correctly. Again, be polite and ask them for help. More flys with honey than vinegar and all that.
Good luck getting it fixed for good!
jb