Forward/ reverse engagement issues with L5030 GST

[VT_Hokie]

I was wondering if anyone has any suggestions before I start looking for the problem or taking it to the dealer.

I have a 2006 L5030 GST that shifts easily into forward or reverse but once engaged the tractor will "buck" like the hydro fluid is being cut off momentarily then back on. It does it 3 to 5 times then everything is ok. Always at least three times. It only happens while shifting from forward to reverse or reverse to forward. Shifting between gears is ok. Also, once it stops bucking I can press the clutch in, regardless of gear and then release it and it will not "buck". So it has something to do with the initial shifting between forward and reverse. To me it sounds like sensor or solenoid is misbehaving. If so which one? I do not have a service manual so if someone can be descriptive with where to look that would be great.

Other. Fluid level fine, 480 hours on unit, 100 since last change. If I increase the rpm then the bucking or jerking becomes harder. PTO and loader work fine.

Thanks for the comments,

VT

 

[David_Kb7uns]

Are you using Super UDT??

David Kb7uns

 

[VT_Hokie]

Good question. I really don't know as it was changed before I received the tractor.

 

[David_Kb7uns]

Well if it is not Super UDT it will effect the shifting.
The GST ECUhas inputs from
Travel speed sensor
Engine Tachometer
GST lever sensor
Shuttle switch
Pressure switch
Trans Temp sensor
The ECU controls the GST valve body and modulates the solenoid going to the clutch pack raising the pressure until it engages.

I would not tear into things without verifying that Super is in there, it may be painful but change the fluid to Super UDT and making sure the filter is a Kubota filter would be my first step. After that you would look at the GST valving as it takes the pistons shifting to send flow to the clutch packs. Getting a copy of the service manual would help you greatly on understanding the system.

David Kb7uns

 

[VT_Hokie]

Just to update the thread, I did the change to SUDT and filter and still have the problem after running it around for a while. The dealer did not have a manual so I will hunt one down somewhere and go from there I guess. It is just interesting that it does it atleast 3 times and up to 5 under load (such as going up a hill) then everything is fine.

Thanks

VT

 

[David_Kb7uns]

Sounding like it is in the oil supply coming from the pump or in the valving.

The transmission gets the supply from the power steering side of the hydraulic pump, then goes through a pressure reducing valve to valve body. After the shift pistons shift the selected gears the pressure in the pilot circuit rises because the shift check valves shut and the clutch valve is actuated and oil flows to low bypass valve and proportional reducing valve to the GST clutch engaging it.

So somewhere in one of the valves or passages something is plugged or the pressure is off spec as it is not doing it smothly like it should. There are some settings in the Intellipanel that fine tune the shiffting for when valves get replaced. I highly recommend getting the service manual as some of the procedures and tests are detailed.

David Kb7uns

 

[VT_Hokie]

Thanks for the description of the flow of things! Will take a look when the manual comes in a few days...

 

[VT_Hokie]

Just to finish this thread, the problem was the pressure sensor for the GST transmission.

 

[lonestar382]

Just to finish this thread, the problem was the pressure sensor for the GST transmission.

My L5030 is having the exact same symptoms. At this point in time, I would like to try and repair this myself. Can you help with where this switch or sensor is located, and any chance you know the part number? Mine will buck 3-6 times, then smooth out perfectly. Thanks in advance for any help you can provide!

Corey Graham
Kubota L5030 GST