L4760 only goes backwards / reverse

[RichHuey]

My L4760 will only go in reverse.
It initially only started when it would get warm. I could always go in reverse but forward would quick fade. If I let the tractor cool, forward would return for a while.

This went on for a couple months. Recently, forward has failed even when cold. Now, even when the pedal in the neutral position the tractor will surge backwards. With the pedal partially forward the tractor will stop, but will not go forward. At start up (requiring neutral HST pedal) the tractor will immediately start going backwards.

I have replaced the pedal potentiometer
Along with the lower pressure relief / check value
Along with the lower HST value

I could get to the lower ones, so I replace them.

No luck so far, almost $1000 in parts...

Anyone have any ideas?

One more symptom is that when the tractor is going backwards it surges significantly

Thanks

Rich

 

[ROBERTL45]

I have an L45 that does the same thing. One additional note is that if you rotate the pedal forward to stop the reverse movement and then turn off the key it will lurch backwards. Please help.

 

[200mph]

It sounds like your problem is very similar to what I experienced and suggest you focus on the HST proportional valves that are used to maintain servo piston position - overall direction and speed control.

HST Issue - Jerky Motion - SOLVED | OrangeTractorTalks - Everything Kubota

There are two of them: Forward (green connector) and reverse is the lower one. Same part number and const about $340 each.

 

[kubotafreak]

Before you change anything else I would run the calibration procedure for the pedal throttle. I don't have access to my l60 Wsm but someone on here will.

 

[200mph]

Very good point about running the fine calibration process mentioned above by kubotafreak.

When going through this process, I experienced error message at times because the servo piston was no longer in the anticipated neutral (center) position. The only way to clear the error during the fine adjust procedure was to replace the proportional valve. At least this was my experience.

The fine adjust procedure is needed any time the input sensors (HST Pedal, Range Shift Lever, Cruise Control Lever, HST Response Dial) are replaced.

Fine calibration = fine adjust mode K in the panel

Since the original poster and has not responded or given updates in nearly a year. Will not contribute to this thread further. ROBERTL45 and I have conversed via phone call about his situation. His symptoms is very similar to what I've experienced in the thread linked in post #3.

 

[kubotafreak]

Let me back up my statement with this caution. You can potentially place the machine in an unusable situation until the issue is fully remedied. However it does not sound like it is usable now so the risk appears to be low…
Are you seeing any code on the intellipannel?