Kubota Bx1800 weird HST problem

[7fayette]

My Bx1800 has a weird problem the dealer has put 40 hours of wrenching time into it and has no idea what is wrong. When the pto is off the tractor does not have any hydraulic pressure causing the hst to make a grinding sound in forward and reverse. It does not matter if it is in high or low. When this happens the tractor has no power and hardly moves, but if you turn on the pto it runs just fine. Dealer has been scratching their heads over this one. Dealer says the pump has a little wear on it, but nothing critical. Thinks it might be the clutch pack. Any ideas?

 

[David_Kb7uns]

Hydraulic pump goes to steering priority valve, until required flow for steering is met nothing goes to loader or back to tank. Next is the steering valve, then it goes to PTO valve and PTO relief valve teed together. PTO relief valve dumps into hydro filter and then that flow goes to the hydrostatic transmission for charge purposes.

Sounds like the transmission is not getting charge pressure fluid and the tranny is running dry. Someplace between the steering valve and the PTO valve/PTO relief valve the fluid is getting dumped but the PTO activation is plugging the leak to build up enough pressure to charge the transmission.

Is the correct hydro filter on?
Is there enough flow from pump?

Just some ideas, oil flow chart in on page 2-M5 in BX WSM manual

David

 

[7fayette]

Hydraulic pump goes to steering priority valve, until required flow for steering is met nothing goes to loader or back to tank. Next is the steering valve, then it goes to PTO valve and PTO relief valve teed together. PTO relief valve dumps into hydro filter and then that flow goes to the hydrostatic transmission for charge purposes.

Sounds like the transmission is not getting charge pressure fluid and the tranny is running dry. Someplace between the steering valve and the PTO valve/PTO relief valve the fluid is getting dumped but the PTO activation is plugging the leak to build up enough pressure to charge the transmission.

Is the correct hydro filter on?
Is there enough flow from pump?

Just some ideas, oil flow chart in on page 2-M5 in BX WSM manual

David

Could the pto shift valve be out of alignment? meaning it is aligned when the pto is turned on, but slightly out of alignment when off causing the dump in pressure?

 

[David_Kb7uns]

Hard to tell by looking at the WSM but there is something going on that is dropping the pressure. From looking at the PTO valve, it is a rotary type and would not know how it could leak from looking at the shop manual.

Here are locations for WSM manuals section 2 is transaxle.

KUBOTA BX18 WORKSHOP MANUAL Pdf Download.

Kubota Bx18 Bx22 Tractor Workshop Service Manual-Searchable

David