2320 Pto shaft is bogging down / slipping !!

[oldnslo]

Orifice might be in the priority flow control valve. I suspect pressure tap would be down stream of the orifice but that is just a semi educated guess. Does the service manual show the valves in exploded views or just talk about them. If that orifice is partially plugged the flow would go to the charge circuit.

 

[mx125]

I can’t find any specific images or home for the priority flow control valve. I’ve attached blow up of the hydraulic pump with senenoid. There is control valve below the rock shaft housing (and next page top the number descriptions).

 

[oldnslo]

I agree that the priority flow control does appear to be in that housing. Per the schematic there is a double pump on your tractor. One section is for steering and implements the other is charge PTO and brake circuit. Is there anything in the hydraulic section showing lines, filter location etc. Per the schematic the line goes from pump to filter and then to priority valve. I suspect the filter is on the transaxle so possibly priority valve is in same area of transaxle. Sorry not much help on where this valve is.

 

[mx125]

The strainer is in the lower rear of transaxle. The filter is visible on the attached. Seems on schematic the drive shaft powers hydrostat separately and there is side gear to power charge pump ( although don’t see that “pump”) which feeds the hydraulic motor. I see where the lines circulate to filter. And see now that the hydraulic motor splits one line to rock shaft and other the pto circuit. But I can’t see where the line or passage is that is opened when senenoid opens. It’s a mystery on diagram. I guess directly below or to side given it’s location on transaxle just above pto clutch.
I also don’t see where strainer fits in as it’s quite far and isolated from these lines. I will add more schematics just in case. And you’re very helpful. This is opening up a lot of knowledge for me.

 

[oldnslo]

Is there another pump somewhere dedicated to charge circuit? It could be part of the hydrostatic pump assembly. I suspect yes but again not sure. I believe what you have posted is the main pump for steering and implements. I believe that is a totally seperate circuit.

 

[mx125]

I’ve attached a helpful (to me) operation page. It seems the charge pump is in centre block and feeds oil at lowish 100psi to all. The hydrostat creates really strong pressure for drive (only) in either direction. The hydraulic pump gets oil from charge pump but does actually seem to only feed steering and implements/draft arms. So you seem to already have that figured out. And the pto circuit gets oil from the charge pump through the flow control valve. So yes ….it is separate it seems. I need to find the flow control valve and orifice. It’s a mystery. And in that area there must be a test port.

How does the oil actually compress pto clutch ? In the disassembly pics of centre case gears, bearings, shafts and clutch plates….it’s all open to case. I don’t understand how or what drives the plates together. Is the oil actuating a mechanical arm? In any case I should check charge pressure as first step. And inspect and clean screen.

 

[oldnslo]

I looked at Deere parts diagram today and they were vague but it almost looked like some extra valves in the hydrostatic motor base plate. Even had one item labeled pump but that looked mislabeled to me. I could find no parts breakdown for the HST pump assembly though or reference to another filter. This sure is a puzzler.

 

[oldnslo]

Looks like we posted at same time. Charge pressure would not show PTO pressure but test ports could be in same general area. The saga continues.

 

[mx125]

Haha yes.
I’ve have the hydrostatic down to individual parts several times (two broken output shafts thanks to siezed drive shaft u joints. There is nothing really there other than check valves. I suspect one of the valves on the centre block (charge pump) might be involved and is close to the clutch. The selenoid is right next to that upper right area.
Does an orifice alone bring 100psi up to 310 for pto without added pump ?

Sorry for all the questions and many many Thanks for all your effort!. I will ask the dealer if they have any secret insight.

 

[oldnslo]

Does an orifice alone bring 100psi up to 310 for pto without added pump ?

Sorry for all the questions and many many Thanks for all your effort!. I will ask the dealer if they have any secret insight.

No the orifice (flow control) just limits the flow going to the PTO circuit the relief valve in the PTO circuit controls the pressure.

No problem on questions and I hope some of my answers are helpful. Good luck at the dealer. They should have specs on procedure to check PTO pressure.

 

[oldnslo]

The PTO clutch is a self contained clutch pack that operates like a spring loaded single acting cylinder. Solenoid energized Pressure is directed into the cylinder which squeezes the clutch plates together. De- energize the solenoid and springs push the plates apart releasing the clutch. Very similar in concept to hydraulic brakes.

 

[mx125]

Interesting. So I suppose the oil feeds through the centre of shaft or channel leading to a pressure plate etc. I couldn’t detect an obvious path in the disassembly pics. I don’t want to split the case, but if I ultimately do….I guess i’ll learn!

 

[oldnslo]

Yes I believe oil is fed through the shaft to the clutch. There are typically several seals on this shaft and in the clutch that could leak but rarely hear about these failing. My first point of attack would be pressure test or if you can find it inspecting the flow control valve. Kubota used similar style valve on BX series and there are some posts about these failing. From memory some where orifice plugged and some where spring fatigue failures.

I hope your dealer can provide additional info on this.

 

[mx125]

Yes I believe oil is fed through the shaft to the clutch. There are typically several seals on this shaft and in the clutch that could leak but rarely hear about these failing. My first point of attack would be pressure test or if you can find it inspecting the flow control valve. Kubota used similar style valve on BX series and there are some posts about these failing. From memory some where orifice plugged and some where spring fatigue failures.

I hope your dealer can provide additional info on this.

Agreed and thank you again.

 

[Erik M]

I have a dealer not 10 km away so I delivered the tractor to them as they were going to likely have to split the tractor to repair the leaking line and replace the burnt PTO clutch pack. They did the pressure test before splitting the tractor which confirmed the leak and the replacement line has a different bracket so that the leak will not reoccur as this was a known issue with this series. While I could likely get the part numbers the dealer will be able to do this for you. If they have to split the tractor to fix the issue get them to inspect the shift mechanism for any worn or damaged parts as it is easy to repair them if the tractor is split. Good luck.

 

[mx125]

I will post another update once i get more detail. I did get advice from dealer…..ran tests. Got a better uderstanding of how this charge pump work. Took off transaxle again…removed hydrostat. Broke down completey and cleaned. Reassembled and same issue.

To clarify function…..
the hydrostatic has 2 spinning piston pumps inside. One for drive and one to drive charge pump. Both dive and suck directly into thick plate with channels. I found port for that pump pressure test ….and the one for the pto Right next to selenoid. Charge should be 100 and pto 300. Mine is 30 and 100. So engages but weak. All of the flow occurs within channels in that one inch thick plate and only one small hole at top That seems to vent oil Into a channel which I assume goes to pto. The return is a line into top of case (not the plate). So i’m lost as to where the pressure is going. Everything works on drive, and separate pump Powers theimplements and steering. Other than weak charge pressure (that keeps oil flowing and driving pto clutch). I can only think the charge pump pressure release is weak, and venting? there is a small valve on side. Removed. Spring is fine. Dealer says that type of issue would be very rare.

So…..I have taken to dealer to see if they can diagnose. He thinks he can In hour or two. But not sure how without full tear own and random parts replacement.?

 

[bgr]

Does service manual provide a schematic for PTO clutch? Can you post a copy of the schematic? Might help us armchair mechanics assist with diagnosis. Charge pump might be the same pump also used for brakes and PTO. Depending on test port location it could read 310 PSI all the time or only when clutch solenoid is energized. Do the brakes work properly? If yes that would indicate that the 310 PSI is available for brakes so would point towards problem in clutch circuit.

The brake referred to is the brake for the PTO drive which sets when PTO is not engaged. The PTO clutch is a multiple plate clutch like an automatic transmission clutch pack. Definitely sounds like the clutch pack is slipping because of low engagement pressure

 

[bgr]

I will post another update once i get more detail. I did get advice from dealer…..ran tests. Got a better uderstanding of how this charge pump work. Took off transaxle again…removed hydrostat. Broke down completey and cleaned. Reassembled and same issue.

To clarify function…..
the hydrostatic has 2 spinning piston pumps inside. One for drive and one to drive charge pump. Both dive and suck directly into thick plate with channels. I found port for that pump pressure test ….and the one for the pto Right next to selenoid. Charge should be 100 and pto 300. Mine is 30 and 100. So engages but weak. All of the flow occurs within channels in that one inch thick plate and only one small hole at top That seems to vent oil Into a channel which I assume goes to pto. The return is a line into top of case (not the plate). So i’m lost as to where the pressure is going. Everything works on drive, and separate pump Powers theimplements and steering. Other than weak charge pressure (that keeps oil flowing and driving pto clutch). I can only think the charge pump pressure release is weak, and venting? there is a small valve on side. Removed. Spring is fine. Dealer says that type of issue would be very rare.

So…..I have taken to dealer to see if they can diagnose. He thinks he can In hour or two. But not sure how without full tear own and random parts replacement.?

Your PTO and charge oil circuits do not go through the hydrostat itself. The charge pump supplies oil to the hydrostat, but PTO pressure is separate from hydrostat although it may go through separate passages in the hydrostat housing. Your test shows low charge pressure. Fix that and you will solve the problem. There could be a leak in a suction line, dirt in the charge pressure relief valve, or maybe the wrong gasket not sealing a charge oil pressure passage. Your dealer should pick up the problem pretty quickly. The gear driving the charge pressure pump is driven by a pin through the input shaft it rides on or a key in a keyway on that shaft.. There may be a problem with that. If the pin is broken or worn the gear may be slipping on the shaft. The charge pump is on the outside of the transmission and can be removed without splitting case. Hopefully the repair can be done without splitting the case.
Let us know what you find out.

 

[mx125]

Thanks for the added info. I do have the official manual. There is a charge pressure port location and proceedure. There is no pto port anywhere in manual. Dealer confirmed it’s not there. He said it would be near pto senenoid and it was. Clearly charge pump pressure low I agree and that issue will solve the other. I also agree seems likely I did something?. there is also no charge pump on outside of hydro. The hydraulic pump is….but only drives implements and steering. I will attach diagram but dual function hydrostat pump. Earlier post with there of op talks about a variable output motor drive pump and the lower fixed output pump inside hydro. Agreed also that high pressure ports and relief valves are for drive. Low pressure circuit is for charge. I did do what I thought was full tear down clean / flashlight etc. including the 3 valves ( 2 high pressure and one I assume is low pressure). Passages were not that tiny and could see through them. the orifice is supposed to be after the charge pump so likely not affect charge pressure. The plug on top of schematic is the charge port test. I remain baffled. I still blame myself…just not sure exactly where it went wrong. Or….given havent used bug cutter this year ….was it just getting weak over time ? Was valve leaking a little ? Prob not i suppose.

 

[bgr]

Thanks for the added info. I do have the official manual. There is a charge pressure port location and proceedure. There is no pto port anywhere in manual. Dealer confirmed it’s not there. He said it would be near pto senenoid and it was. Clearly charge pump pressure low I agree and that issue will solve the other. I also agree seems likely I did something?. there is also no charge pump on outside of hydro. The hydraulic pump is….but only drives implements and steering. I will attach diagram but dual function hydrostat pump. Earlier post with there of op talks about a variable output motor drive pump and the lower fixed output pump inside hydro. Agreed also that high pressure ports and relief valves are for drive. Low pressure circuit is for charge. I did do what I thought was full tear down clean / flashlight etc. including the 3 valves ( 2 high pressure and one I assume is low pressure). Passages were not that tiny and could see through them. the orifice is supposed to be after the charge pump so likely not affect charge pressure. The plug on top of schematic is the charge port test. I remain baffled. I still blame myself…just not sure exactly where it went wrong. Or….given havent used bug cutter this year ….was it just getting weak over time ? Was valve leaking a little ? Prob not i suppose.

I have removed my post which referred to the wrong transmission for your tractor. The two hydro "pumps" are actually just parts of the hydro. The hydro does not supply oil pressure to anything else. The hydraulic pump in one of your parts pics which is on the outside of the case is the charge pump, it supplies oil to all other services and it supplies 100 psi charge pressure to the hydro trans. Its pressure is controlled by the charge pressure relief valve. It does supply the PTO circuit per your schematic and that is why the PTO solenoid is close to that pump. The reason for low charge pump pressure is either an air leak in an intake line, a bit of dirt in the charge pressure relief valve, a problem with a gasket or wrong fit in the hydro which causes a leak of some of the charge oil coming in, or some problem in the gear on the input shaft from engine which drives a gear on the charge pump.(Not Likely.) The most likely cause is a small leak in an intake line due to your service with Oring or gasket not quite sealing. Pressure relief problem is second.(Did you find and check the charge pressure relief valve.?) Third some error in hydro assembly causing a small leak of charge pressure. Finally, did you see the gear train which drove that oil pump from the input shaft when you took hydro off or did that remain untouched? Could you have problems with how the gear is secured to input shaft or how gear is secured to the pump input shaft? Did you have to take the charge pump off or apart to work on the hydro? Most likely, a gear problem would give no pump output at all from charge pump. Partial pressure is likely to be sealing problem of relief valve or a small leak somewhere.
I don't believe this is a problem which existed before your work. The clutch will work OK after charge pressure is fixed unless it was run for a long with reduced apply pressure.