Kubota BX2200 HST Shudder - Barely Moves

[TjsMi]

Hello All,

Thank you in advance for reading this.

I have a BX2200 with ~1200 hours on it. Purchased about two years ago and has ran great ever since until now.

The issue I am having is that the tractor will barely move in forward or reverse. When I press on the pedal, it shudders very badly and moves slowly. If I throttle up, I will lose all movement and it will sit there like I am in neutral. FEL, PTO and three point hitch are working well and seem to have full strength.

The first indication that there was a problem was ~month ago while mowing. After mowing for 45 minutes or so, the HST started to lose power and shudder a little. MMM and FEL still worked well. Once I let the tractor cool down, it seemed to be OK again. After that I changed fuel filters. Next time I mowed the same thing happened. I then changed the transmission filter thinking it may be clogged. The next time I used it I was brush hogging. The same thing started to happen so I shut down the brush hog and started back for the barn. Half way there the tractor just stopped in its tracks and wouldn't move. I was able to limp it back by feathering the HST pedal.

Below are thing I have done after reading various forum posts.
-Checked fluid levels
-Cleaned Transmission Strainer - was very little in it
-Checked transmission cooling fan. It was intact and spinning as expected.
-Checked HST pedal linkage. I am not 100% familiar with the linage setup, but when I press the pedal it seems to be moving the input to the transmission to its full allowable travel.


I have the WSM and based on the troubleshooting guide I am thinking of checking the charge relief valve pressures next. Thinking the pump is probably fine since all other hydraulics work fine.

Anyone else had this experience? Any suggestions?

Thanks,
Tom

 

[oldnslo]

Does your BX have a single pump with priority flow control for steering?

If yes does the steering continue to work when HST does not? If yes again check the charge relief since the steering flow is also charge flow.

If I remember correctly the PTO also operates off the steering charge circuit.

 

[TjsMi]

Hi - thanks for the reply.

Yes, BX2200 has single pump with priority valve. My power steering (and PTO) work fine went HST does not.

I値l take your suggestion and check the charge relief. I値l have to pick up some fittings and pressure gauge to do so.

Thanks.
Tom

 

[TjsMi]

Quick update on this:

I picked up some fittings and checked the charge relief pressure. It is low (only about 20 PSI compared to spec of 40-70). Additionally, I checked the PTO relief pressure, which is upstream of the charge relief, and it is also low. The high pressure side of the system (power steering, loader and lift) all seem fine.

I replaced the flow priority valve as some other forum posts indicates that that may be the cause, but there was no improvement.

I am sort of thinking of replacing PTO and Charge relief valves next since these control the pressures of the circuits that are indicating low
Pressure. But, I am not super confident that is the issue since all the pressures after the power steering circuit all seem low. Also, I have a hard time believing both the PTO and Charge relief valves both failed at the same time.

Would there be anything in the power steering circuit (upstream of charge circuit) that could cause the downstream pressures to be low, without impacting the performance of the steering (since it seems fine)?

Any other thoughts?

Thanks in advance.
Tom

 

[skipperbrown]

Call the service manager at your closest dealer and ask him for advice. He may or may not be very helpful. I do all my work, but buy my parts at a close by dealer. The service manager has always been helpful with suggestions.

 

[oldnslo]

How low was the PTO pressure? I don稚 remember the circuit on how the PTO & charge relief valves are plumbed. If in series the charge being low would make the PTO a similar amount low.

 

[TjsMi]

Thanks for the reply.

The plumbing For the path that leads to the transmission is as follows:

Pump—>Flow priority valve —> Power Steering (Spec 1400 PSI) —> PTO Clutch Relief (spec 138 PSI)—> Transmission filter —> Hst Charge (Spec 40-70 PSI)

As you pointed out, the PTO pressure is low by about the same amount as the Charge pressure (25 PSI). After my last post I attempted to shim the charge relief valve to increase charge pressure, but to no avail.

Since I have already replaced flow priority and hst transmission filter+ Strainer, I am starting to think It must be something internal to HST preventing charge pressure from building. The troubleshooting guide in the WSM also points that direction. So looking pretty likely that HST is going to need to come out.

 

[oldnslo]

Tom,
Does the travel speed slowly decrease as tranny warms or up or is speed loss a sudden change? Slow change with temperature increase would point towards internal leakage in the system. Sudden change of travel speed is more puzzling.

Are you checking pressures with oil cold or heated up?

 

[aczlan]

Have you tried letting you get warmed up, then disconnect one of the loader lines and put a couple quarts into a bucket?
Something like that could be caused by a leak on the suction side of the pump so it's sucking in air with the hydraulic fluid.

Aaron Z

 

[TjsMi]

In general, the situation has been slow decrease in travel speed as the tranny warms up. Most recently it was a sudden change of travel speed which is what prompted me to start digging into this. Maybe it had been leaking internally and whatever the cause just got bad enough to cause sudden change.

I am checking the pressure cold right now....haven’t tried heating it up.

Thanks!