John Deere 2850 -gearbox

[Captain Jack Sparrow]

Hello, hoping some can help please.
Tractor wont go into reverse , nothing there at all, but it drives forward in every gear.

I've removed the rear wheel to expose the linkage,found and uncoupled the reverse linkage. There was no resistance from the shaft going into the gearbox, it was just loose and floating about.

We're not frightened to tackle it, but need to know where we're going.

Any ideas please???

 

[agri knives]

I was in a Jd dealers workshop 25 years ago, and the mechanic showed me a box of small bearings that give trouble in the gearbox, he said only for that problem he would be out of work, so maybe it’s the same problem that you have , if it is it’s a big job, cab off .

 

[njneer]

Cab off , top lid off and you will be able to see the selectors and forks and see what’s wrong.
Be careful removing the lid as it presses down on the springs for the detents on the rail , easy to lose the springs.
it may just have come loose on the selector fork.
From memory some of the selector rails may slide enough to remove the forks but some you will need to split it to get them out.

 

[BlueBrick81]

We have had the top off our 3050 and its fairly simple on the inside, cant remember exactly how the selectors and the linkage works but it will simple to work out. while its off check for ware on the rear circlips on the end of the top shaft. But be warned parts for the gearbox are very expensive.

 

[holwellcourtfarm]

Does this help to visualise it?

Grabbed from here: https://partscatalog.deere.com/jdrc/sidebyside/equipment/81680/referrer/navigation/pgId/185375458

 

[Tractor Tim]

Happened to me years ago apparently there is a roll pin that holds a arm on the shaft in the gearbox similar to the one on the outside of the that can break or come out. Hopefully a simple fix

 

[Tractortech]

Now Then..
As said, it's a cab off job. It's rare to just loose reverse.. The hollow shaft (No8) sometimes breaks but that usually gives difficulty with low range too. I've also seen the pads of the selector fork where it sits in the selector collar wear away. No29 is the low range / reverse selector, you'll have to split the tractor to replace it. When you lift the rockshaft off, lift it off level unless you have the swing over tool. It doesn't hold any balls or springs, nothing will jump out at all. Balls and springs are in the front bearing quill. There's a technique for disassembly and reassembly..
Also, there are no roll pins holding anything together. All the arms on the shafts are splined and retained by a grub screw in a groove. There'll not be any loose screws in the selector folks either, they're all loctited in and are used for fork adjustment. (Only if someone has previously been in and put it together badly will there be anything loose)
Spend some money while it's in bits, some things wear with age, take the opportunity to prevent future failures..

 

[MontyK]

Cant remembere which is reverse but could be that the hollow selector shaft has snapped seen it before, top cover off, not too bad a job.