Kubota L3901 4X4 HST VS GST Transmission

[David_Kb7uns]

The Grand Ls had

FST Fully Synchronized Transmission. The transmission with synchronizers on the gears for shifting while moving.
GST Glide Shift Transmission Electro-hydraulic shifting synchronized gear transmission.
HST Hydrostatic Transmission. Hydrostatic drive transmission with gear ranges.

The Economy L series has listed a HST and the Synchro-Shuttle which should be the unsynchronized gear but has the synchros on the shuttle for forward reverse on the fly but still must stop to change speeds.

David Kb7uns

 

[FTG-05]

The Grand Ls had

FST Fully Synchronized Transmission. The transmission with synchronizers on the gears for shifting while moving.
GST Glide Shift Transmission Electro-hydraulic shifting synchronized gear transmission.
HST Hydrostatic Transmission. Hydrostatic drive transmission with gear ranges.

The Economy L series has listed a HST and the Synchro-Shuttle which should be the unsynchronized gear but has the synchros on the shuttle for forward reverse on the fly but still must stop to change speeds.

David Kb7uns

So, putting it in layman's terms, and in the same order:

- Manual transmission, use clutch pedal to shift gears
- Manual transmission, transmission shifts gears
- Automatic transmission with high/low

How close did I come?

 

[k0ua]

Did they change transmission on the geared 3301-3901? Because the 3200-3800 were non-syncro geared. Just curious.

from the kubota brochure:

Gear Drive Transmission with Synchro-Shuttle (F and DT
Models)
You'll finish the big jobs easily with the mechanical Synchro-Shuttle
Transmission featuring inline forward and reverse shifting for quick
directional changes. The transmission offers 4 main-shift speeds and 2
range-shift speeds (Hi/Lo) for a total of 8 forward and 8 reverse
speeds (8FX8R), enabling you to select the right speed for better
productivity.

 

[k0ua]

So, putting it in layman's terms, and in the same order:

- Manual transmission, use clutch pedal to shift gears
- Manual transmission, transmission shifts gears
- Automatic transmission with high/low

How close did I come?

Close but not quite on the Hydrostat.
People think of it as an automatic transmission, but if you are comparing it to an automatic transmission in a car or truck, no not really
it is something else entirely.

remember automatic transmissions have gears (execpt CVT's) Clutch packs and torque converters.

A hydrostatic drive system in simple terms. (there is always more) has a hydraulic pump driven by the engine a swash plate and an hydraulic motor to drive the final drive gear train. Many will have 3 gear ranges behind the hydraulic motor, but some only two. You control pressure delivered to the hydraulic motor by adjusting the swash plate with the foot controls. Here is a video that can help.

https://www.youtube.com/watch?v=qxZFSNITK-c

 

[kubotacres]

from the kubota brochure:

Gear Drive Transmission with Synchro-Shuttle (F and DT
Models)
You'll finish the big jobs easily with the mechanical Synchro-Shuttle
Transmission featuring inline forward and reverse shifting for quick
directional changes. The transmission offers 4 main-shift speeds and 2
range-shift speeds (Hi/Lo) for a total of 8 forward and 8 reverse
speeds (8FX8R), enabling you to select the right speed for better
productivity.

So from assumption this means that the range selector can be shifted while not completely stopped like the Grand L's and the gear selection will have to be stopped. Next time I stop by my dealer I'll check this out.

 

[k0ua]

keep in mind that the hydrostatic system is infinitely variable ground speed for a given input speed from the engine within the range of possible speed. Unlike an automatic transmission in a truck which has a finite number of gear ranges that are selected by clutch packs. If you want to go exactly 2.1280763 miles per hour, you can do that with a hydro while lets say your engine is turning 2000 RPM. Now with the exact same engine RPM of 2000 you can adjust the swash plate angle to now make the tractor go 1.928503 miles per hour. and if you want to change direction and go in reverse at 1.928503 miles per hour you just change the swash plate angle the other direction passing through the neutral position to make the hydraulic motor run in the other direction because the flow direction of the fluid is reversed. With an automatic transmission in a truck, you cannot go 1.928503 miles per hour and 2.1280763 miles per hour with a fixed engine speed of 2000 RPM. The speed in the automatic transmission are fixed for each given RPM and each gear the transmission is in. The GST transmission is actually closer to the automatic in your car or truck than the Hydrostatic transmission is.

 

[k0ua]

So from assumption this means that the range selector can be shifted while not completely stopped like the Grand L's and the gear selection will have to be stopped. Next time I stop by my dealer I'll check this out.

Check it out and report back, but I think it just means there are synchronizers on each gear to make engagement smoother,(align the teeth) like synchronizers in a car transmission. I believe you will still have to clutch to change directions and even ranges on this transmission, unlike the Glide shift.

 

[FTG-05]

Close but not quite on the Hydrostat.
People think of it as an automatic transmission, but if you are comparing it to an automatic transmission in a car or truck, no not really
it is something else entirely.

remember automatic transmissions have gears (except CVT's) Clutch packs and torque converters.

A hydrostatic drive system in simple terms. (there is always more) has a hydraulic pump driven by the engine a swash plate and an hydraulic motor to drive the final drive gear train. Many will have 3 gear ranges behind the hydraulic motor, but some only two. You control pressure delivered to the hydraulic motor by adjusting the swash plate with the foot controls. Here is a video that can help.

https://www.youtube.com/watch?v=qxZFSNITK-c

When I said layman's terms, I was referring to how it's operated by the operator, not the internal technology. I wouldn't know the different between a clutch pack and a torque converter if they both walked in here and bit me on the you-know-where!

Having said that, a very good sweet synopsis!

For some reason, my PC won't play youtube videos right now.

What does this mean: "You control pressure delivered to the hydraulic motor by adjusting the swash plate with the foot controls"? The foot controls speed up or slow down the tractor?

 

[k0ua]

When I said layman's terms, I was referring to how it's operated by the operator, not the internal technology. I wouldn't know the different between a clutch pack and a torque converter if they both walked in here and bit me on the you-know-where!

For some reason, my PC won't play youtube videos right now.

What does this mean: "You control pressure delivered to the hydraulic motor by adjusting the swash plate with the foot controls"? The foot controls speed up or slow down the tractor?

Yes, correct. when you press on either a rocker (treadle pedal, Kubota brand and some Kioti's) or one of the twin pedals for most of the other brands and the more expensive Kioti's, you control the ground speed by pressing harder on the pedal. Lets give an example of the Kubota system, either the standard hydro or the hydro plus: Start engine, and lets say set the RPM at 2000 and leave it there. There is no foot throttle only the dash mounted control. Now push forward on the treadle peddle, and the tractor moves forward, the harder you press, the faster it moves (within its range). Now you want to go in the opposite direction just as fast. Rock the pedal backwards with you foot, the tractor stops, (real darn quick I might add, if you do it rapidly) and you go just as fast in the opposite direction. Of course if you operate it smoothly it will be extremely smooth. If you operate it harshly it will be harsh.. OK so far so good?

 

[k0ua]

What you are doing is adjusting the angle of the swash plate with the peddle/peddles. If you press NO pedal, the tractor stays in Neutral. It just sits there even though it is ready to go. If you press a peddle direction then take your foot off the pedal it returns to neutral by itself. So if your silly azz falls of the tractor it just stops (as long as it is not pointed downhill).