I own a 4 month old John Deere 5100E that I bought new. So far, the A/C only works on cool days. Also there is no recirculate switch so the air is always pulled in from outside in extremely dusty conditions so if I run the A/C then I have to change or clean the filters each day. The reverse does not work. Transmission will flash N if I try to put it in Reverse. From the first day that I tried to use the PTO, it doesn't hold pressure so approximately every 60 seconds, the implement will have fallen to the ground and the pump will kick in and the implement will jump up but then fall down again. From the first day, the brakes don't work unless I pump them twice. If I forget to pump up the brakes in the morning and then also during use, I won't have enough pressure to stop the tractor. Recently, I drove into an arroyo when using a rotary cutter because I couldn't see the arroyo until I was right on top of it so I had time only to hit the brakes once and that wasn't enough to stop it. Fortunately I had the hay spear installed on the loader and it caught on the opposite side of the ten foot deep but narrow ditch. I was able to use the loader to push back from the arroyo and was able to extricate myself from the ditch. Remember I don't have reverse. The pneumatic seat doesn't hold air and the switch to add air is difficult to reach so I have to stop work so I can add air. It's been in the shop for a week and they haven't found time to look at it yet. It has 78 hours on it and I just asked the dealer if they want it back. I hate to let them repossess it but the reason I bought a new tractor was because I was tired of working on worn out equipment.