JD 820 rockshaft not lifting and slow to drop.

This weekend, when I took a break after several hours of running my PTO bush hog on the 3 point of my 820, the rock shaft would not operate. I made sure it was on the top setting #1 (Load?) but it still would not lift the 3 point. I tried the other settings and nothing. PTO was operating normal, as was and is the tractor. So, I drug the bush hog back to the shed on its skids, disconnected it, and drove the tractor to the garage for diagnosis. There is plenty of hydraulic oil, in fact it looks like I overfilled it last time I replaced the filter and cleaned the screen (possible cause to issue?).

The new hydraulic pump I installed several months ago seems to be working as the brakes are nice and stiff, and when I look into the hydraulic oil fill port I can see hydraulic oil squirting onto the final drives. Furthermore, after letting it idle the rock shaft did function and raise. Not sure, but this may have only occurred after I screwed down all the way the drop rate control as prescribed in the Technical Manual. However, when I opened it back up the shaft did not lower at the usual speed. Many minutes later I noticed it did eventually lower. I removed and inspected the drop-rate control thingy as prescribed, but did not see anything obviously wrong. No obvious leaks anywhere.

Does this sound like a clogged transmission oil filter? Transmission oil pump? A dump valve issue? A rock shaft seal issue?

As always, any help is much appreciated.
 

L is load sensing when using ground engaging tools. All other functions setting be in D for depth control. Brakes don't operate from hyd pump pressure. Trans pump just replenishes oil in brake valve housing.

How many hrs of use since filter was changed & suction screen checked?

Check frt pump coupler to be sure pump shaft is turning with engine CS.
 
She had less than 50 hours on the filter, screen cleaning, and tran oil, but I changed it anyways as the first step of diagnosing this problem. Found some good sized chunks of steel in the bowl of the filter. Yes, the pump shaft is turning with engine crank shaft.

However, it didn't fix it. Now, it seems that not only will the rockshaft not operate, but there is no longer any hydraulic oil squirting on to the final drives. My thought is that this indicates either that the pump has failed, or that one of the valves is stuck, as I believe that this is an open center system and that if everything is in neutral the fluid should be flowing out the two tubes on to the left and right final drives viewable through the fill port. Yes?

So, I figure the next thing to check is the dump valve. I will be taking it apart ASAP. Then the two other valves right in front of it. Maybe one is a bypass valve in case filter is clogged and maybe the other is thermal, but I cannot recall, and I don't have the Technical Manual here at work.

Any ideas about what some of the more common causes of this problem that I am looking for? I imagine valves clogged with debris or blown seals to be two of the more likely faults, yes?

This post was edited by hedgeless_horseman on 05/25/2022 at 11:19 am.
 
So, I executed the third diagnostic for "Rockshaft - Fails To Rise Or Rises Too Slowly" in my JD Technical Manual, image attached. By sticking my phone camera in the observation port, I could clearly see that the return spring of the operating lever is not visible through the observation port, photo attached, and that the linkage does move when the engine is not operating. The TM states that this means I need to hook in spring or replace it, and provides step by step instructions on how to open up the rockshaft to do so. Now, I just need to go pick up a new spring, the gasket for the rockshaft housing, and a JD 244-2 lifting eye so I can hoist it.

PS: When I was mowing the pasture, I clearly recall hearing a loud ping from the tractor (over the noise of the engine, bushhog, and with earbuds in) and wondering what it was. I now think it was the spring coming off or breaking.

mvphoto92511.jpg


mvphoto92512.jpg

[/img]

This post was edited by hedgeless_horseman on 05/26/2022 at 05:44 am.
 

Sounds as if you're on correct repair path. One doesn't need JD244-2 eye to lift rockshaft housing. Just place correct size bolt with large washer through chain link into hole designed to bolt seat frame to RS housing to lift housing.
 
My local JD dealer has the gasket and spring, but is not able to find anything for the lifting eye. Anyone have any idea of the part number or threading so I can use a bolt and washer?
 
Bolt that secures seat frame to rockshaft housing is 1/2'' NC threads in diameter Tell your JD parts personnel that way back in 1965 when I 1st started being a dealer parts personnel that I learned that the 19H in bolt part # indicates standard grade 5 bolt with course threads

mvphoto92514.png


This post was edited by Tx Jim on 05/26/2022 at 08:02 am.
 

Well, unfortunately, after opening up the rockshaft I can see that the spring I thought was either broken or disconnected is neither.

Next step in the Technical Manual is to replace the o ring and back up ring on the piston.

Good times!
mvphoto92546.jpg


mvphoto92547.jpg
 
At this point, is there a way that I can go back and truly confirm the hydraulic pump is functioning correctly, not just that its driveshaft is spinning, with the rockshaft disassembled?
 

You can check hyd pump output by engaging starter but it will be messy!

If hyd pump is operating oil will be expelled from hose shown in your photo & orifice in RH frt side of trans case where quad ring is located in trans case recessed area
 
I disconnected the lines at the hydraulic pump, ran the engine, and it appears that no hydraulic oil is getting to the hydraulic pump which appears to be operating correctly. No leaks in the suction line.

My take is that either the bypass valve is stuck open because the spring is too weak, or the transmission pump has failed. I am picking up a new spring and valve to try tonight. If that does not work, then I must split the tractor between the clutch and transmission to get to the shaft-gear-driven transmission pump.

Does anyone have any experience with a failed transmission pump similar to the one on the 820? What am I looking for?

Thanks,
h_h

This post was edited by hedgeless_horseman on 06/13/2022 at 09:41 am.
 
Before splitting the tractor, which I have not ever done before, I wanted to be as certain as possible that the problem is the transmission pump. So, following the advice of a couple men wiser than me, I drained the tranny fluid, [i:863ca2de15]again[/i:863ca2de15], put the drain plugs back in, but not the screen, filter and housing, or the relief valve of the clutch housing, nor the tranny pump bypass valve for which I replaced the spring and body. I then poured diesel in the tranny case to clean it, which quickly flowed out the open screen plug, letting me know that portion of the system is not blocked.

Next, I replaced the screen, poured in more diesel, and nothing came out of the open filter or valve orifices. I started the tractor and still nothing. I replaced the bypass valve and added more diesel to the tranny case, which then started slowly leaking out the relief valve orifice in the clutch housing. I replaced it. Added more diesel, and started the tractor again, but still no flow out of the open paper filter orifice.

My understanding is that the transmission oil pump is what sends the oil through this filter and then on to the hydraulic pump. By getting fluid to flow through the pre-filter screen, but not through the paper filter, I can now be fairly certain that the problem is indeed that the transmission oil pump is faulty.

Is my logic and process sound?
 


You test is correct if pto shaft will operate when clutch pedal is up & engine crankshaft is turning. IIRC pto driveshaft splined into pto clutch hub powers trans pump
 
I was able to split the tractor between the transmission and clutch, remove the pump and shafts that drive it, and clearly see that the problem is that both gears of the transmission oil pump are completely broken. Surprisingly, the roller bearing and pump housing are still in good shape. Replacement gears and o-rings ordered.


mvphoto93546.jpg


mvphoto93547.jpg
 
It's never easy. I received the two new gears, and filed the burrs and rough spots in the case as instructed in the TM. However, they still catch when I spin them by hand, such that I am pretty sure this is what caused them to break. So, I ordered an entire new pump with case, gears, and bearing, and returned the gears.
 
New transmission oil pump installed and turns smoothly.

However, I am having problems getting the two halves of the tractor back together. My wife and sons are starting to think I don't know what I am doing!!! Worse, they are starting to give me advice!!!

Please help.

I have the rear on blocks and the front on a hoist.

I can get it to the last couple inches, but no further. The only thing touching is the top shaft shaft inside the hollow shaft going through the pump, which I can get started into the bearing on the front of the transmission. I can also get the outer shaft seated into the pump and its bearing, which I think indicates it is all the way seated forward into the clutch housing, because it will no longer spin with the engine being off.

The rear end of the solid shaft is started into the tranny, and the big front tranny gear is started onto the splines of the outer drive.

It is just this last 2 inches I cannot close. I rock and roll the rear, and have also now killed two Hi-Lift Jack cleavis trying to force it together.

Please, what are the pearls and pitfalls for closing the last bit?
 

One should attempt to ""finesse tractor halves together NEVER FORCE together"".

Have you tried putting trans in a speed selection while turning engine crankshaft & pto in gear while attempting to turn rear pto shaft in an attempt to align shaft splines??
 
(quoted from post at 03:14:34 07/02/22)
One should attempt to ""finesse tractor halves together NEVER FORCE together"".

Have you tried putting trans in a speed selection while turning engine crankshaft & pto in gear while attempting to turn rear pto shaft in an attempt to align shaft splines??

Well, I wish I would have known that earlier, before breaking two clevis attachments. lol

I can imagine how to put tranny into a speed selection, like say 1st gear. I can also imagine how to turn rear pto shaft. But how would I turn the engine crankshaft in this instance? Would I need to, if I can align the shafts from the rear? Does pushing in the clutch help?
 

Having rear half of your tractor on blocks makes rejoining halves more difficult. In your situation one can press against fan belt & rotate fan to turn engine crankshaft. Also 2 correct diameter bolts with heads removed can be used as guide dowels to assist in aligning halves.

When I supervised/assisted splitting tractors rear half was supported by a a stand with a caster wheel. When halves were close we placed trans in highest gear & rear tires rolling turned trans shaft to align splines.
 
The problem appears to be that the solid/inner shaft cannot move forward into its position up in the clutch area. When I remove the shaft and shine a light in there I can see that the orifice in whatever (rust colored/clutch component?) piece it is supposed to go through at the front end, beyond the splines for the outer shaft, has moved such that only a portion of the orifice is still showing at the end of the tunnel.

I tried moving the clutch pedal but that didn't seem to help.

Any ideas? Am I going to need to now also split the tractor between the clutch housing and the engine?
 

If you depressed clutch operating pedal when trans input shaft was removed from clutch hub then you're going to have to split between engine & clutch housing to realign clutch with pilot brg.
 
Since I am going to be in the neighborhood, should I replace anything? Disk? Throw - Out Bearing?

Also, this is clearly wishful thinking, but is there any hope of not splitting the tractor into three? For example, by aligning the hole in the clutch by sticking a broomstick or some such thing through the shaft tunnel into the portion of the orifice still showing and then pressing the clutch pedal enough to allow the stick to pass through and center the orifice?

This post was edited by hedgeless_horseman on 07/05/2022 at 08:49 am.
 
I hear you. Am I going to need one of these clutch alignment tool thingys?

https://www.yesterdaystractors.com/John-Deere-820_Clutch-Alignment-Tool-1-x-15-and-1-1-2-x-23-Spline_156040.html
 
Because I had already split the tractor between the tranny and clutch the actual shafts were free to use to align the clutch, so I didn't need the dummy shaft tool. Leaving the assembly in place on the flywheel, I just loosened the six bolts holding the clutch pressure plate on, stuck both shafts in together, and everything lined right up. I tightened the bolts back down and only then removed the shafts. Closing up the front split between clutch and flywheel/engine went smoothly.

However, when it came time to try to close up the rear split between clutch and tranny I encountered the exact same problem as before, where I could not seem to get the outer hollow shaft far enough forward into its clutch, even though I knew both plates were in close alignment. I did not press the clutch pedal this time - lesson learned. I removed the new tranny pump and loosened the bolts on its housing, mounted the new pump all the way on to the outer shaft with the inner shaft extended as far as possible, pushed the inner shaft all the way forward into its clutch, and then pushed and jiggled (because it now had some play) the outer shaft with its pump assembly into its clutch, thanks be to God!!! Then I could bolt in the pump and tighten down its housing after the shafts were fully seated.

When I rejoined the two halves, it went pretty smoothly. I had purchased some longer bolts to act as guides, as Jim suggested, and aligned the well greased splines simply by turning the crankshaft the smallest amount at the front drive shaft to the hydraulic pump.

We will see if it all works after I get the gear shift levers, rock shaft, lines, wires, and linkages all reconnected.
mvphoto94413.jpg


mvphoto94414.jpg
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top