jd 850 pto question--doesn't ease into gear

[Willl]

What's this stuff that Paul was talking about in his above post ?

Does this '850' have a standard PTO setup like other plain jane non-hydraulic tractors ?

 

[Niji]

I guess so. It's a manual gearbox, no frills. I've done plenty of mechanicking, but never been inside a transmission, so I'm not visualizing the working parts yet.

It is possible this is just an incredibly abrupt pto to engage, and nothing is technically wrong with it. That's what I'm hoping to find out here. Or else find out that something might be done to improve the situation. But having grown up my entire life with tons of tractors of all kinds, I can honestly say I've never seen anything so sudden on the pto of any brand , size, or age.

 

[Rara Avis]

What's this stuff that Paul was talking about in his above post ?

Does this '850' have a standard PTO setup like other plain jane non-hydraulic tractors ?

The 55 series stuff had the delay system...I wasn't sure about the 50 series...

 

[irwin]

The 55 series stuff had the delay system...I wasn't sure about the 50 series...

Hi Paul, no delay, but I think the 850 came with a single stage or two stage clutch, at least that was the option for the next generation (670, 770, 870).

With a two stage clutch you should be able to feather the pto engagement just like you can feather the transmission engagement. (about 1/3 way up on clutch pedal travel)

The pto does not disengage with pushing the clutch.

It's possible the pto part of a two stage clutch could be stuck together, or maybe you have a single stage clutch.

 

[Trac-Tech]

I'm not too familiar with this tractor, but if has a two stage clutch, have a look around the bell housing for an inspection plate. If you find one, remove it and trun the flywheel around gently and there will most likely be an adjustment for the 2nd stage. There should be three at even intervals around the flywheel. I think this may be a Japanese Yanmar painted green? Please forgive me if I am wrong. If it is, it will need adjusting to 40thou or there abouts. I used to work on Iseki tractors many years ago and the two stage clutch which is still used today in cheaper basic units is still used no matter what the brand. A copy of the clutch is even used in some Kioti/Daedong models out of Korea as well.
All the other ideas of oil on the plate can be the problem as well as the 2nd stage being out of adjustment. The 2nd stage gets out of adjustment as the main clutch wears and hence the reason for poor disengagement. If you have a loader fitted, you may have to remove the subframe to get to the inspection plate, but that depends on the loader manufacturer.
Best of luck.
P.S. if it is a Yanmar, drop me a line and I may be able to help with some info a little more reliable than my memory and guess work!!
Cheers

 

[Niji]

Thanks for the input from OZ! The diesel motor is definitely a Yanmar. It is 4 wheel drive. I don't know about the rest of the tractor, accept to say it is JD green and serial numbered. When finding parts, there are 2 sets of numbers with different listings, and this is the newer model (post 200,000 if I remember right), and I do have a loader.

I'll go have a look with your notes in mind and see what it looks like. It would be fantastic if I could discover a 2 stage clutch in there for the pto.

 

[Niji]

I thought I posted the superb results a little bit ago, but I must have hit the wrong key as I don't see it up here--so here goes again:

I went out and opened up that access in the bell housing, and while that didn't help me much, I discovered a little bit of play in the clutch pedal linkage. Not much...the pedal had to be depressed about an inch before it started really moving things inside, so I adjusted the threaded rod to take up that slack and suddenly, miraculously, I have a 2 stage clutch that works the pto!

I'm a really happy camper. Thanks for all the various insight here on the forum helping me getting this sorted out. I have no doubt my transmission's life has just been greatly increased!

 

[irwin]

I went out and opened up that access in the bell housing, and while that didn't help me much, I discovered a little bit of play in the clutch pedal linkage. Not much...the pedal had to be depressed about an inch before it started really moving things inside, so I adjusted the threaded rod to take up that slack and suddenly, miraculously, I have a 2 stage clutch that works the pto!

Fantastic!

Sure sounded like the clutch(s) were malfunctioning. Good for you.

 

[Trac-Tech]

Hi Guys
Good to hear that you are making some progress, but I am sorry to have to be the one to burst your bubble. The pedal needs that play between the where the pedal is completely released to where you feel some weight. Preferably the more the better. If you remove this "freeplay", you are effectively doing the same as resting your foot on the pedal when driving. This is not good!!
If you look in the inspection hole again, there will be three bolts screwed into a steel plate with a lock nut on the bolt screwed up tight against the plate as well evenly spaced around the flywheel (1/3-1/3-1/3). These bolts are horizontal and usually with the head to the rear of the tractor. The head of the bolt will be either 1/2" or 12mm and the nut will be either 1/2" or 13mm There will be another plate at the head of the bolt and the gap between the bolt head and the plate is what needs to be adjusted. Due to wear on the main clutch plate, the gap between the head of the three bolts and the plate mentioned earlier will be too wide and take too much pedal travel to get them to do their job. Once you have found one of the bolts, get some one to press the pedal while you watch what happens inside, you will get the picture of what you are trying to achieve then.
When I dont know what the gap should be adjusted to, the method I use is as follows: -

1. Adjust the freeplay on the pedal so as to have enough that when the pedal is fully released the thrust bearing will not be contacting the fingers on the clutch. You can see this through the inspection plate normally if you look towards the rear of the tractor inside the bell hsg.
2. Loosen the lock nuts and adjust all three of the bolts so the gap is greater not less.
3. Press the pedal down to where you would like the second stage to start, this is normally when the pedal is about 80-85% of the way down to the floor.
4. Tie the pedal with some wire at this point to ensure that it stays at the same height through out this adjustment.
5. Then screw the bolts outwards until the head of the bolt just comes into contact with the plate mentioned earlier.
6. Tighten the lock nut and move on to the next one and repeat the process untill all three are adjusted the same and the locknuts are secured.
7. Release the peadl and replace the cover.
8. Test the clutch is disengaging correctly without grating.

Normally you would just use a feeler gauge and adjust them all to the same one by one. As an example, the Iseki I was talking about was 40thou, MF135 etc 60thou, David Brown is 1/8" etc. Please be carefull that the ignition key is off and any other precautions that can be made so the tractor cannot inadvertently start while your fingers are in the hole. Never seen or heard of it happening and would rather stay that way thanks.
If any one reading this can give me an idea of the equivalent Yanmar model, I can probably help with definitive inof rather than relying on my mechanical aptitude and bad explanation.
All the best, but please dont leave the pedal without any free play.
Cheers

 

[Niji]

It was just too good to be true.

I'll adjust the clutch rod for the pedal back this morning and see if I can get the clutch adjusted inside the bell housing as you describe. The access hole is rather small, and it is difficult to see much, so it may be quite a trick. This one is on the left side of the bell housing at about the height of the footboard, and is about the size of a thermostat cover on a V-8 motor--in fact, the gasket looks identical to most thermostat cover gaskets, and so the access is about an inch and a half square.

Wish me luck.