GST transmission

[Henro]

<font color="blue"> I wonder how well the electronic solenoids will last many years down the road?...I think the electronics could be as problem in many years to come! </font>

littlediesel,

After decades of experience with electrical/electronics systems in the industrial environment I share you concern about electronics on tractors! I really hate the thought of a electronic dash panel or perhaps even an on board computer... /forums/images/graemlins/blush.gif

But there is a difference between electronic controls and electric solenoids. Solenoids are proven, relatively simple devices that if properly designed and manufactured can last for a VERY LONG time. I have seen mill equipment that was installed in the late 40's still working reliably up until a couple years ago, when it was shut down. But even then it was still working and ready to go for who knows how many years to come, if given the chance?

Assuming the solenoids employed in the GST shifting system are well made and designed for the environment they find themselves in, there is really no reason they should be too great of a concern. These things are simple electro-mechanical devices. Very rugged, very simple, very reliable.

Certainly do hate the thought of high tech on tractors though. KISS rules in my mind... /forums/images/graemlins/smile.gif

 

[slowzuki]

And to answer the fellows question, forward reverse is clutchless too I believe like a hydraulic shuttle.

In ag tractor terms its is like a hydraulic or electric shuttle combined with 12f/8r powershift.

Ken

 

[SkyPup]

Don't worry about how long these amazing GST transmissions will last when maintained properly, people asked the same thing about the HST's when they first came out too over twenty five years ago.....

The two main important things for maintaining a GST tranny are using Super UDT hydraulic fluid to insure low hydraulic filter backpressure and always keeping a fully charged battery as a defective battery can destroy or alter the ECU operating the tranny.

 

[smittyd3]

I have a L3130 GST with 3.8 hours on it. (If the dealer had a 3130 with the regular transmission I would have picked it instead ot the GST). I too share your concern. I emailed Kubota support about 2 weeks ago about the GST transmission along with the 6 solenoid warnings.

The Kubota support person called me at work last week. He told me if the solenoids were a problem the dealers were not reporting it and he assured me they would. As it has already been stated in this thread, he said use the super udt and follow the maintenance schedule and you shouldn't have any problems.

I haven't used my tractor because I have to get the correct quick coupler for the bucket, (the tilt cylinder rods hit the boom when dumping the bucket), but as soon as the dealer gets this "fixed", I'll trying out my new tractor.

 

[SkyPup]

Smitty - our L3130 GST has almost 600 hrs of extreme duty on it using Kubota Super UDT hydraulic fluid without a single problem.


Taken from “New Features of the Kubota Grand L30 Series Compact Tractors”

The Glide Shift Transmission (GST) is original Kubota technology which provides 12 forward and 8 reverse shift-on-the-go gears without the need for clutch operation. The GST has a hydraulic clutch and transmission gears that are changed by the action of an actuator located in the transmission. When the operator initiates a gear change, the GST automatically performs a series of operations that includes disengaging the hydraulic clutch prior to the gear change, changing the gears and then engaging the hydraulic clutch after the change.

The ECU allows for a single shifting lever that actuates a potentiometer signifying the specific gear selection. In the Grand L30 series tractors, the ECU controls a proportional pressure reducing valve, solenoid valves, and performs a gear change by operating a hydraulic clutch.

With this GST system the pressurization of the hydraulic clutch can be set by a proportional pressure reducing valve for limitless stages, all of which is controlled by the ECU. The tractor is equipped with an engine tachometer sensor and a travel speed sensor, as well as a potentiometer that distinguishes the position of the gear selection lever. Based on digital signals from the engine tachometer sensor and the potentiometer, travel speed after the completion of a gear change is calculated, while the travel speed sensor calculates the actual travel speed. Based on the difference between the two speeds, the pressurization characteristics of the hydraulic fluid supplied to the clutch is set. Thus the Kubota GST brings about a smooth gear change by changing the pressurization characteristic in response to the various patterns of gear operation.

Acceleration of the tractor is calculated based on digital signals from the travel speed sensor. Under conditions when the tractor accelerates rapidly, the pressurization is changed to become slower during the pressurization process. When the tractor accelerates slowly, the pressurization is changed to be more prompt.

After the hydraulic clutch begins engaging and the acceleration of the tractor starts, the acceleration is calculated and the pressurization characteristic is compensated. Tractors may be equipped with a variety of different implements according the context of work users wish to perform. In particular, when an extremely heavy implement is attached to the tractor, acceleration does not occur until the compensation begins, which makes gear change time much longer. Therefore the compensation of the pressurization characteristic based on the total tractor weight is realized. The offset can be input using the “Adjustment Mode” of the IntelliPanel, with the correct offset stored in ROM. The ECU of the GST takes in the correction value by communicating with the ECU of the IntelliPanel and compensates the pressurization characteristic.

 

[WhiteRock]

Great write up! Thanks! Very interesting.

I don't think I would be worried about the solenoids. Sounds like they control hydraulic needle valves and are probably extremely reliable. Things I might worry about would be wires, dirt in the potentiometer. All wire need to be securely encapsulated. I suspect they are. I have sticks and brush move my safety interlock switches and remove pin clips, lynch pins, etc. very annoying. I have taken to cable tieing them on. The potentiometer is probably hermetically sealed with a bell crank on it.

The ECUs have a pretty good record in cars now. So I imagine Kubota has that down pretty good.

 

[SkyPup]

The potentiometer is located at the bottom end of the shift lever on the left hand side way up from the undercarriage. It is sealed, as is the ECU, and there is no where on the tractor when you cannot spray water. The entire undercarriage is clean of communication wires as well as exposed hydraulic lines, that is one thing I specifically inspected prior to purchase as I saw alot of exposed internals on the JD and NH competitor models knowing full well that they would get ripped out during brush work.

There are alot of diagrams explaing what the text outlines, giving more specific information of the process. Other manufactures have used GST type hydraulic clutch trannies but Kubota has incorporated theeir proprietary pressure reducing valve to smooth out the clutch engagement, which no one else has at the present time.

I cannot state how important it is to utilize Super UDT hydraulic fluid and keep a fully functional battery to keep the L30 Series tractors operational. Short cutting either of these two will decrease the long term usefulness of the enitre rig.

 

[smittyd3]

Thanks for the information SkyPup.

 

[littlediesel]

Skypup,

Very Good!! /forums/images/graemlins/shocked.gif Where did you learn all that? /forums/images/graemlins/confused.gif

Jon

 

[SkyPup]

Kubota publishes engineering reviews of their product designs in peer reviewed engineering publications in various professional organizations.