John Deere 4840 Tranny Troubles

John Deere 4840 1 Problems

I blew out a U joint on my John Deere 4840 and the input shaft in the transmission was bent. Doubled than 0.020. with it’s all back together. I have a vibration at low revs that seems to disappear at higher speed. Will it run this way or is it going to gouge more joints?


  • A new guy who did that, we took out the front and rear driveline and used a jack and put it in place, it took some time and you have to be careful. When we finished we checked it with a dial indicator and it was almost perfect. Maybe we were lucky.
  • If you have a PTO you cannot remove the front cover on the tractor. So I would say find a shop with a lift or a dealership and take it out and fix it. If you take it out there are some updates that can be done without taking it all apart. How many hours does the tractor have? It’s too bad you’re not in eastern Washington, it would be a two-day job.
  • There is an update on the low clutch package and not all dealers know about it. It would be easy to do if you take the trany off and have the clutch off. The other upgrades are some snap rings that upgrade from two pieces to one piece but you have to take the entire trany apart to do it. I bet the reason the trany was over transported was that the retaining ring on the low clutch pack came off. With the updates, a transmission of more than 10,000 hours is made.
  • If you don’t have a book here are some things that will help. Leave the lines hooked to the two main hy pumps and just unbolt from the front of the trany saves time and a hassle. The transmission mission pump stays in the transmission. To remove it from the tractor you have to tilt the front of the transmission with a long arm and lift it at the same time. Pto transmissions are a bit tighter. Be careful, the transmission weighs 2400 pounds.
John Deere 4840 2 1
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