About to buy: GST vs. HST

[bilrus61]

When you outlined your uses what struck me was the 5 acres of tilling. I am sure it depends on soil type but my GST tractor doesn't travel slow enough, for my tastes, when tilling in my soil.

MarkV

Really MarkV? Which GST tractor do you have? My L5040GST, at rated speed, (2600 RPM) travels 0.9 mph in first gear. I usually run my tractor at 2100-2300 RPM when tilling and almost never in first gear. 3rd gear is the standard gear I till with. I'm tilling with a JD 660 chain drive/L tines tiller that is 63 inches endplate to endplate. I sometimes till in 4th gear if soil conditions are just right and sometimes will drop to 2nd breaking tough wet gooey sod.

Just checked and a 60 inch mower (we'll pretend it is a tiller just for giggles) mowing/tilling at 0.9 mph doing 5 acres would take 10.1 hours. Yikes thats a lot of tilling time! If you went slower with a HST...say 0.5 mph it would take 18.2 hours to till 5 acres. Oy my aching butt.

 

[MarkV]

Really MarkV? Which GST tractor do you have? My L5040GST, at rated speed, (2600 RPM) travels 0.9 mph in first gear. I usually run my tractor at 2100-2300 RPM when tilling and almost never in first gear. 3rd gear is the standard gear I till with. I'm tilling with a JD 660 chain drive/L tines tiller that is 63 inches endplate to endplate. I sometimes till in 4th gear if soil conditions are just right and sometimes will drop to 2nd breaking tough wet gooey sod.

Just checked and a 60 inch mower (we'll pretend it is a tiller just for giggles) mowing/tilling at 0.9 mph doing 5 acres would take 10.1 hours. Yikes thats a lot of tilling time! If you went slower with a HST...say 0.5 mph it would take 18.2 hours to till 5 acres. Oy my aching butt.

Well I have a Kubota L39 which is GST and a Kubota B21 which is HST. Both of these models are from Kubota's commercial TLB line so gear ratios may be much different than other variations of the GST models. In my red Georgia clay my GST runs too fast in 1st gear in an established garden bed for my taste.

I am sure it has to do with soil conditions and gear ratios on the tractor model. Larger tractors don't offer a creeper gear option because no one needs it. I just felt it was worth checking if you were going to till 5 acres on an annual schedule.

MarkV

 

[Grandad4]

Hydro trans are nothing like automatic transmissions in modern automobiles. A GST trans is a closer equivalent to automatic automotive transmission.

Wasn't trying to say an HST was "like" an automotive AT; sorry if you got that impression. But, even though they operate quite differently, both HST's and AT's share the common traits of being a bit less mechanically efficient than a manual tranny and having owners who don't mind because they are otherwise more convenient to use.

 

[johnk]

I have a GST and I have to admit I never drove a HST. I do a Lot of loader work and box scraping and haul down the road to help out my neighbors. I drive up some very steep trails at my place and feel very safe going up and down them. I'll stick with what feels good. Not a lot of noise and more efficent as I have read...

 

[crazyal]

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 é„*djustment 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. The offset is just a derivative of the diameter of the tractors tire diameter.

This is from a different thread but I thought I would post it here.
http://www.tractorbynet.com/forums/newreply.php?do=newreply&p=1024011

 

[k0ua]

Oh one other thing I do not like about the HST. When going down steep grades it will get faster as the HST isn't as good at holding the tractor back. On my 5040 GST you make the turn with the bushhog running full RPMs and head downhill and you can feel the gears hold the tractor back and maintain a more constant speed. Much more secure feeling for me than my mom's B3030HST. Weeeeeeeeeeeeeee!

Well I cannot speak about a B3030HST, but I can speak to an L3400HST, and I have a hill I work on a lot (the road) that is as steep as any I have ever seen. It is dangerous to walk down if your feet hit gravel you can easily fall. And I can tell you this if you center the Hydro pedal in the L3400HST, rapidly you can find yourself stopping very rapidly The braking on this hydro by just rapidly letting off of the pedal is major. You can skid the tires easy. You quickly learn to make smooth moves on a hill like that with the Hydro by letting of smoothly. Now the hydro in the lawn mower, a JD will NOT hold you back going down that very same steep hill. It tries, but you will need some brake to keep from going Weeeee... But it is just a little thing with a big fat guy on top of it:laughing:

There is nothing "wrong" with gear, GST or Hydro, I just happen to love hydro, because of the way I use the tractor, mostly loader work, and let me tell you, there is nothing better for loader work. Foot on pedal, right hand on loader control, and left hand on the wheel.

James K0UA

 

[crbr]

Okay, I think I'm about to finally upgrade from my John Deere 870 and am looking at Kubota L4240 or L4740. I thought I was going HST but I visited my brother last week he he's trying to talk me into going with the GST transmission (he owns an L5030 GST).

My current tractor uses:

Mow about 15 acres with a Caroni TM1900 flail mower. I might be switching to a bush hog as I think it fits my "rough" property better. Hopefully most of this land will be converted to pasture soon so I will have much less mowing to do!

Rototill/cultivate about 5 acres for market gardens (various veggies). I also use a single bottom plow and 6 ft. disc harrow some but mostly use rototiller for soil prep.

Once I get more animals I will have more manure to "move around". (i.e. loader work) I also have several large compost piles that I turn with the loader.

I guess my biggest concern with the HST is with the ground engaging equipment - tilling. Yes, I've read all the threads and most people say the HST can handle this no problem.

However, I have been told that when tilling with an HST and going slow the tiller can actually "push" the tractor forward. This was also confirmed by my Kubota salesman. Has anybody actually experienced this when tilling?

I've driven my brother's GST tractor and like it ok but really was looking forward to the features of Kubota's HST+ transmission. Will I be happy with HST given my tractor uses?

I'd not consider anything other than a HST. It's a proven component time and time again.

 

[Johnbro]

I went from 20 years on a shuttle-shift geared Kubota (L2250) to a L4240 HST and I would never go back to a geared unit. Loader is a slam dunk win for HST but in my mind mowing is superior as well since you can adjust the wheel speed completely independent from the engine speed. That is simply not possible with any non-hydro tranny. I have very rough, hilly 5 acres and do a lot of careful creeping with the tractor. In the 2250 mowing meant a lot of clutch work, with the HST it's a piece of cake.HTH.

 

[kubotadriver4life]

A GST trans is a closer equivalent to automatic automotive transmission.

I don't understand. HST uses oil to transmit power as does an automatic tranny in a car....right? With HST there is also infinite amount of possible speeds, which and Auto tranny in a car does. How would a gear drive with hydraulic shifting be more comprable?

I want to make sure i have this right.

GST:
hydraulically shifted gear transmission. It is able to shift up or down on the fly without using the clutch. They just use a hydraulic actuator to eliminate the need to stop the tractor and clutch into a different gear. Correct?

HST:
A hydraulic pump that the displacement can be varied, that then drives a fixed-displacement hydraulic motor. Correct?

 

[Alan L.]

I don't consider tilling ground engagement. To me ground engagement is pulling a bottom plow or disk. Tilling speed is infinitely controlled with an HST and FEL work is easier with an HST. Now, I am saying this having never used a GST tractor.

My tiller doesn't push my tractor at all with the HST and it is really too big for the tractor. If you have this concern you could get a reverse rotation tiller.

I can understand why GST would be better in applications where you need a precise, unvariable speed.