HST: Rabbit versus Turtle

[tmc2318]

Whenever I'm using my tractor for tilling I will usually run my HST tranny in LOW (turtle) speed then shift up to HIGH (rabbit) speed to turn around. I am wondering if I show just run in HIGH all the time or will I be 'wasting' power or lugging as you would in a higher gear. This may seam obvious but it is not like gearing as the HST tranny is constantly-variable as I understand it.
To put it another way - If I'm tilling at say 0.5 MPH @ 2500 RPM in turtle speed does it matter if I am in rabbit speed with the same 0.5 MPH @ 2500 RPM? I always use my cruise and adjust accordingly to get the 0.5 MPH. It's obvious that I would have less power if I shifted the gearing from L to M but does it matter with the HST ranges as well? Should I be running in high or low for tilling to get maximum power to the tiller or does it matter if I am at the same speed?

 

[Muskrat84]

I am just a novice when it comes to tractors, but to me it would seem that you wouldn't have the torque needed to till in high range. I would also think the extra heat you are creating would not do your tractor any favors when it come to longevity. I could be wrong, that's just the way I perceive it.

 

[gotcha]

I am just a novice when it comes to tractors, but to me it would seem that you wouldn't have the torque needed to till in high range. I would also think the extra heat you are creating would not do your tractor any favors when it come to longevity. I could be wrong, that's just the way I perceive it.

I totally agree with Muskrat's answer. That is the reason they put a high, med, and low gears in tractors. Low for slow speed and TORQUE and high for speed and mostly speed alone.
The Gotcha Man

 

[DavidAubke]

There is a definite torque difference between high and low range. Low range is not just a way of limiting the total available speed.

There have been several times where I ran short of power before realizing I'd left it in Rabbit mode.

 

[DavidAubke]

After reading your question more carefully, I have to admit, I don't know the effect the range shifter has on the PTO. While the range only applies to the drive wheels, I have to assume that it's still akin to running in a high gear. Your engine is working harder than it needs to thereby lowering the total power available to the PTO.

 

[SouthernConservative]

When running any PTO implement - I always use L or turtle - I can control the speed with the amount of pressure on the HST - I NEVER use the H or Rabbit unless I am traveling the 2 miles to additional property - and even then I don't go "all out" on the HST - Let the tractor work in the correct range and you will be fine - tilling, shredder work, FEL work all should be in turtle.

If you have 4x4 use it only with FEL work and heavy pulling..

 

[art]

I'd run in the middle range and not be doing any range changes.

That is the plus of the three range transmission that you still have good power in the middle range as well as good ground speed.

Tillers don't require much pulling force for forward turning tines but even the reverse tine tillers won't drag a 3030 down.

 

[dodge man]

I think in theory, you could run in high range, be using less HST pedal and being running the "same gear ratio" overall. I think in practice, running in low gear gives you alot more control with the HST pedal and you will be less likely to be lugging the engine.

 

[J_J]

Is not the PTO speed based on the speed of the engine, and when tilling, you are supposed to run the PTO at 540? Therefore at the same engine rpm, you will have the same HP to the tiller, and the effect of changing speed range is to move forward a little slower or faster. Just depends on the quality of the tilled earth you want. One go round may be enough at slow speed, while cross tilling at med or high speed may give some good results. Rules are rules, but they can be broken. Is it worth changing transport speed to get around to the end of the row, and how do you do your rows, up and down , side by side, or do a field from the outside in, putting the tractor in a smooth turn at the end of the row. I see a lot of tractors doing a 90 degree turn, then a 270 turn to come back down the side of the previous row, and thought what a lot of lost motion. It's just time, I suppose.

 

[KeithInSpace]

Whenever I'm using my tractor for tilling I will usually run my HST tranny in LOW (turtle) speed then shift up to HIGH (rabbit) speed to turn around.

I probably wouldn't mess with that. I off-load stone off my trailer in Low, and there it stays UNLESS I'm driving the load another 200/300 feet across my yard, when the time saved by stopping and shifting the tranny is made up by my vastly swifter progress across the yard.

If I'm tilling at say 0.5 MPH @ 2500 RPM in turtle speed does it matter if I am in rabbit speed with the same 0.5 MPH @ 2500 RPM?

It probably does matter, especially if you're working against the implement. If you're in a 'no load' condition on the tractor, I don't think it'd make a hill of beans of difference, but when working against a load (reverse spinning tines of tiller), I think of it as holding a car with an automatic transmission against a hill using the gas...eventually things start heating up beyond the cooling capacity of the transmission.

My rule of thumb? If I'm performing a function that REQUIRES me to stay below the top speed of my low range, I stay in low range. Or if I'm performing a ground-engagement function that forces me to push the treadle down more simply to maintain a ground speed against growing resistance, I stay in low range.

When running any PTO implement - I always use L or turtle - I can control the speed with the amount of pressure on the HST - I NEVER use the H or Rabbit unless I am traveling the 2 miles to additional property - and even then I don't go "all out" on the HST - Let the tractor work in the correct range and you will be fine - tilling, shredder work, FEL work all should be in turtle.

If you have 4x4 use it only with FEL work and heavy pulling..

Wow...your name says it all...Conservative. Don't ever put the "treadle to the metal"? I actually think it is easier on the transmission to have the full benefit of fast flowing fluid. No fear should be had in putting the treadle to the floor.

And as far as PTO engagement only in low range...I have a Kubota PTO-driven impeller bagger and mow in high range...never had a problem with that.

And only using 4X4 in those particular circumstances? I have a spot in my yard that requires me to engage 4WD as I mow...a steep spot that happens to be slippery with clay and almost always wet. What about down a steep wet hill? Or travelling across a muddy, slopping parking field? All things I've done.

I just wouldn't generalize so much. The different functions on the tractor are to help out in vastly varying conditions. Otherwise, they'd call the "4WD" lever the "FEL and Ground Engagement" lever. Or have a sticker next to the PTO, "Only Engage with Drive Transmission in Low Range".