Using PTO in high range?

[torch]

My tractor has 2 rear PTO speeds: 540 and 857 rpm (@ 2800 engine rpm). My backhoe manual cautions "The backhoe has been designed to operate in the 540 PTO-RPM position only. Do not operate in the 750 position or backhoe hydraulic system damage may result."

Ok, so >540 rpm = bad thing. I get that. The relief valve probably can't keep up with the flow or the fluid will overheat or something.

But is there any reason not to operate in the high range, with the engine throttled down to limit the PTO below 540 rpm? I have a laser tachometer, I can dial it in effectively. I'm thinking it would be quieter, more fuel efficient and easier on the engine.

I may find that the engine lugs down because it's not putting out full HP, but we have very sandy soil around here. Easy digging. And if it doesn't work I can always go back to the low range and rev up the engine.

Thoughts?

 

[mendonsy]

I don't have a backhoe so I can't answer your power question, but I always run my 5' bush hog and 54" snow blower with the PTO on high and the throttle at 1800 rpm. As long as you have a HST transmission it shouldn't be a problem for most attachments.

 

[Workerbee]

I think that might work ok. Up here in heavy snow country we used to hook 540 rpm blower gearboxes up to 1000 rpm output shafts and run at low engine rpm with great results. But we used 100 hp tractors or larger so the power wasnt any factor as it might be on your little tractor.

 

[rjcorazza]

I ran my B8200 in the high speed PTO at reduced engine rpm all the time when mowing.

 

[Roadworthy]

If you throttle back to lower your PTO speed you will not be getting the full power from your engine. Keep the engine speed in the suggested PTO range or you may find yourself overworking the engine.

 

[chim]

A couple tractors back I had a B7500 that had a selectable PTO RPM. I tried using the RFM on the higher speed with the engine slowed down. The tractor bogged down because it didn't have enough power to run the mower and the HST.

 

[GreensvilleJay]

you'd have to throttle back to 1764 RPM and probably lose a LOT of power(aka torque) as you're now about 60% of the desired 2800RPMs.
Maybe someone has the 'power curve' charts that shows RPM vs torque ??
The big issue is WHAT does the implement NEED to run ? The label should say xxx hp @ 540 RPM. I leave it to the math wizzes to do the calculations....

 

[SidecarFlip]

My one M9 has a 2 speed PTO (540-1000) and I use the 1000 position only in reduced engine rpm and run 540 implements but even with my M's, reducing the pto speed to 540 in the 1000 position reduces the torque to a point where the engine isn't capable of pulling a sustained implement load.

I have almost 90 pto ponies and even with mine, it's not enough.

 

[PHPaul]

I don't understand what you expect to gain. Lugging a diesel is never a good idea and I can't imagine you'd get a measurable increase in fuel economy. It's not like diesel is all that expensive at the moment.

 

[SidecarFlip]

Exactly.

 

[torch]

you'd have to throttle back to 1764 RPM and probably lose a LOT of power(aka torque) as you're now about 60% of the desired 2800RPMs.
Maybe someone has the 'power curve' charts that shows RPM vs torque ??
The big issue is WHAT does the implement NEED to run ? The label should say xxx hp @ 540 RPM. I leave it to the math wizzes to do the calculations....

You raise some interesting points. There's no label on the machine or notation in the manual indicating the requirements. However, it is listed by Kubota for my tractor (among others) but the slightly bigger version is not, so let's assume my tractor meets the minimums, although I'm not sure if that's based on engine power or tractor weight and size.

I've not seen a torque curve for the tractor, but the B7100 uses the Kubota D750-A engine. Google says maximum HP is 16.5 @ 3,000rpm. However, maximum torque is at 1800 rpm. Right around where I want to be to get 540 PTO rpm in high range. Cool.

So I tried it out. Took it over to the field and dug out a couple of small tree stumps in high range but throttled down to give me 540 rpm on the PTO. Worked quite well in the sand. I hooked one tree root and it started to lug down the engine, but it was also dragging the bucket edge and stabilizers towards the hole so more power wasn't the answer there anyway.

I don't think it would be as successful blowing snow though. I need enough power to blow the snow and propel the tractor up the hill at the same time! Maybe if I was just touching up after a light snowfall, but not our normal events.

 

[torch]

I don't understand what you expect to gain.

This little guy is not too hard on fuel, true. But there is a noticeable difference between consumption at full throttle and consumption at 3/4. Blowing snow at full throttle, I get maybe 5 or 6 hours between refills. Using the loader to play in the dirt at lower throttle settings and I can go all day and more.

That said, the biggest advantages I see are reduced noise and wear-and-tear on the engine.

 

[SidecarFlip]

I should add that my 2 speed 540/1000 pto is also 2 different output shafts. The 540 is a 6 spline and the 1000 is a 21 spline so if I use the 21 spline I have to add a 21-6 adapter to run a 540 implement in the 1000 pto position. I mainly use it for stationary drive when running a grain leg which isn't power intensive anyway.

 

[Greg8352]

This little guy is not too hard on fuel, true. But there is a noticeable difference between consumption at full throttle and consumption at 3/4. Blowing snow at full throttle, I get maybe 5 or 6 hours between refills. Using the loader to play in the dirt at lower throttle settings and I can go all day and more.

That said, the biggest advantages I see are reduced noise and wear-and-tear on the engine.

Fuel here today 2.05 I have 3 PTO speeds and run everything at 540. Tractor over 40 years old and I have liked it so far!

 

[torch]

Fuel here today 2.05

2.68 up here, by the time I convert litres and dollars. Still, a fair bit cheaper than it was a year ago.

 

[GreensvilleJay]

another comparison..
say you're pulling a heavy trailer with your pickup. along the flat highway ,you're in overdrive,great fuel economy. when you get to the steep,long hill you HAVE to downshift,1 or 2 gears, to get the power to get up the hill. So you trade fuel economy for power.

 

[Palmettokat]

Not orange but JD has what they call "economy" pto option on several model tractors. I had one with about 90 gross hp. It works like the OP is asking about and worked great for proper loads. I mainly used it with sprayer but that was about only pto power it was used for. Yes made big difference in fuel use and yes higher rpms equal more rpms which equals more engine wear. However most home owners of small tractors see low hours so wearing out probably not much an issue compared to true commercial use. At same time will not use my L6060 to spray for it does not have the "E" pto and use my older B2710. It has very low hours for it's age.

 

[torch]

another comparison..
say you're pulling a heavy trailer with your pickup. along the flat highway ,you're in overdrive,great fuel economy. when you get to the steep,long hill you HAVE to downshift,1 or 2 gears, to get the power to get up the hill. So you trade fuel economy for power.

Yes. I get that. Referred to the concept in my initial post. I would equate digging in that clay you folks in the Golden Horseshoe "dirt" to driving up the steep hill whereas the Muskoka sand I'm sitting on seems closer to a long flat superslab.

I found this in the manual:

"The 4600 Series Backhoe can be operated at any
engine speed from 1800 to factory rated RPM, in
the 540 PTO-RPM position. The backhoe is most
efficient at full engine speed. However, in easy
digging conditions, or in residential neighborhoods
where noise may be a consideration, the engine
speed can be lowered to 1800 to 2400 RPM based
on performance requirements."

Not orange but JD has what they call "economy" pto option on several model tractors. I had one with about 90 gross hp. It works like the OP is asking about and worked great for proper loads.

Interesting. That led me down another Google-based rabbit hole ;-)

It does sound like the same concept, except JD automatically limits the engine speed to maintain 540 PTO rpm. One test showed fuel savings between 15 and 27%, depending on the specific model. Another site suggested that dust ingestion of the air filter was reduced due to lower intake air speeds.

 

[mikester]

The rule of thumb is Don’t Lug the Engine...it’s also written in the manual. If you can operate in higher gear without lugging then you are probably going to be ok. Ideally you want to be in the peak power range of your engine for best efficiency.

 

[shootem604]

My L245DT has 3 PTO speeds, and I often use the 2nd range (720 PTO RPM) just at lower engine speeds. The engine doesn't lug down at all even under heavy use, and no hydraulic issues.