Kubota HST in Low Med or High?

art · Nov 26, 2007

I like the middle range for digging over the low range. In low it is far to easy to over power the tires with horsepower and spin as you stated.

I like to use the middle range at about 2/3rds throttle to dig with for most all types of digging. The transmission will whine when under load and that tells me it's time to get moving the loader or back off the petal. I've watched people who hold there foot in there to loang and cause the tractor to stall and if you are stalling then I don't know where you would need more weight. If it didn't stall and would just spin like in low range then I'd say you need more weight.

When the engine goes to die get off the petal and start raiseing the loader as it probably is letting you know the bucket is full.

Racer71 · Nov 26, 2007

Thanks guys.

My tires are filled and I have the 450# box on the back. The ground is sand and the R1 just dig into it. I may buy a toothbar this week.

You can see what I am digging into on the righthand side of the picture up top.

john_bud · Nov 26, 2007

Well, if the ground is loose sand, it's hard to get solid traction no matter what. Still, I'd up the rear weight to 800-1000# carried low.

jb

art · Nov 28, 2007

I disagree with the suggestions here, weight is not a problem, slow down on the hydro petal, raise the loader faster with bucket rollback at the same time. You are going into hard pack dirt, even a five ton payloader can have trouble here.

patrick_g · Nov 28, 2007

I have lo, med, and hi range HST. Hi range is essentially for roading or level ground (hardly will start the tractor moving if slight upgrade)

Med is most often used for any dirt work except if Box blade is full and has to go uphill or FEL is digging into tough stuff then Low is used but Med is 90% solution.

I truly envy everyone who can use loaded tires. Man that would be great but unfortunately is prohibited for my model. I have all the cast iron wheel weights Kubota allows on the rear wheels and usually carry a brush hog or box blade for ballast (without which the FEL is essentially useless for picking up much.)

I have a carryall which I have never hitched up in 5 years but am thinking I will make it into a weight platform to get more weight on the rear tires without sticking out so far in back as to make for maneuvering problems like the brush hog does. I'm thinking a 55 gal drum filled with scrap concrete and then poured with concrete. That should improve traction fairly nicely without a maneuvering penalty. Alternatively I could just build a 3 PH capability onto a 55 gal drum and save the carryall for some other experiment.

Pat

ovrszd · Nov 29, 2007

Anytime you are applying pressure on the HST pedal and the tractor isn't moving or spinning it's tires you are heating up your HST system. This isn't good.

It would create the same effect if you could start a load with your automatic transmission car or pickup in high or 2nd gear. You wouldn't even consider doing that even if it were possible.

Again, remember, pedal pressure and no movement is a BAD thing!!!! If you had an HST temperature gauge you would see immediate climb in temps when doing that.

I run a trans temp gauge on my auto trans Jeep and can create 20-30 degree rises in temps within a couple minutes of gas pedal and no movement conditions. Not a good thing!!!!

john_bud · Nov 29, 2007

Ovrszd has a good point, but an HST operates vastly differently from an auto's trans. The no movement in an HST, is caused by the pressure relief valve opening and bypassing the fluid back to the tank. That is the same type of situation that happens when you over load your FEL (or come to the stops). I don't panic when that happens. Sure, it heats up, but not fast and not catastrophically.

When the autotrans isn't moving (with the gas peddle down), the torque converter is slipping. Different action to the fluid entirely. Much more aggressive agitation of the fluid and much more heat is generated. Orders of magnitude more.

I won't tell anyone to put the hst in high range and a push on a huge tree, but don't be overly concerned if you stall forward motion in high. Just switch to medium and get about your business.

jb

patrick_g · Nov 29, 2007

Right on John, Shear forces on the fluid in the torque converter create lots of heat real quick. The local heating where the shearing is taking place is way more intense than you will see on a gauge because the gauge is not sampling the temp where the heating is it is sampling the fluid temp after it is mixed with some of the cooler fluid (in most installations.)

I recall the old drag racing days where you put the auto trans in low gear, put your foot down hard on the brake, then apply full throttle ("power stall" is one term), and then to leap off the line you release the brake. Fast start. Not good practice if you want long maint intervals. Not too severe if if you don't hold at the line too long waiting for the Christmas tree to trickle down to a start signal.

The hydrostat is quite different from a torque converter or just about any car or truck trans for over the road use. The hydrostat pedal adjusts a swash plate or equivalent such that the stroke length (and derivatively the volume) of a hydraulic pump is controlled by pedal position. If you just press the pedal a little then the pump stroke is short and the volume of fluid sent out is small. Pressing the pedal farther increases the the length of the stroke of the pump and increases the volume of fluid pumped per stroke. Short or long strokes, the number of strokes per unit time is a linear function of the RPM.

If you stall the unit, i.e. try to push down the BIG tree in high range, then the required pressure to move forward is greater than the pump will produce/allow and it will bypass rather than stop the engine (usually.) I kill my engine all too frequently when using the brush hog to eat trees larger than is reasonable. Also in high range I can't even start the tractor moving if it is on more than a slight upgrade. I have learned to stop closer to parallel to the contour lines if I want to take off again in high range.

One of the small nits I have with my Kubota is that it needs 4 ranges, not 3. High is often too high and medium is often too low. Sure, just take a chill pill and be patient using medium but with an intermediate range to high and medium I'd be happier.

Pat

638 · Dec 5, 2007

I would suggest a change in your technique. Enter the spoils pile slowly, and when the bucket is about half way in, start rolling the bucket up and lifting the bucket at the same time. Continue driving forward and this will slice a 2 to 4 inch layer off of the front of the spoils pile. I almost always never spin a tire and always have a full bucket using this procedure. Takes a while to master, but it works for me.

ron

bkheur · Dec 6, 2007

638 said:
I would suggest a change in your technique. Enter the spoils pile slowly, and when the bucket is about half way in, start rolling the bucket up and lifting the bucket at the same time. Continue driving forward and this will slice a 2 to 4 inch layer off of the front of the spoils pile. I almost always never spin a tire and always have a full bucket using this procedure. Takes a while to master, but it works for me.

ron

Good to see someone else from southern Indiana.

I agree. Size the job to the tractor. I live by a coal mine and even a Cat D-9 or D-11 Dozer can be stalled. It takes a whole lot but it can be done.