L3700 PTO Noise - Normal?

[Chilly807]

The owners manual says to "Engage the PTO at reduced engine speed to avoid shock loads to the PTO". It does not define what "reduced" is so the wording definitely leaves some room for interpretation.

BTW, I know the noise is not coming from my rotary mower blades or gear box. The noise definitely emanates from below the drivers seat somewhere in the driveline.

Could anyone with a later model L3400 or L3700 that either does or has engaged their PTO at idle speed tell me if they get the same clatter/rattle/knock that smoothes out at RPM's increase?

thanks,
Steven

In general, I try to engage the PTO at the lowest speed that the engine won't stall, and that varies from one implement to another depending on the amount of inertia they have. My rotary cutter and drivetrain is noisy (Land Pride 1860) at idle. The PTO power pulses aren't smooth enough at idle for smooth operation, until you get up to about 1100-1300 rpm when things even out. Essentially what is happening is the engine is trying to spin the cutter, then the cutter is trying to spin the engine. I can engage it at idle if I'm careful with the clutch, but I probably bump it up 100 rpm or so before engaging.

The post hole auger is smooth as silk when engaging, even at idle, it has much less inertia to overcome. Also, it has an under-driven gearbox, output speed is less than input. The rotary cutter is over-driven, the output speed is greater than the input.

As for engaging the PTO at full PTO rpm, that's the same as engaging the transmission in your car at the engine rpm you normally drive on the highway. Very hard on clutches and driveline, and something I personally would not recommend. You're asking the cutter, which has considerable inertia, to instantly spin up to full speed. A hydraulic drive can cope with that to a certain degree, but a friction clutch isn't going to do well long-term under those conditions.

If yours is an HST, I'd recommend engaging the PTO at just above idle, enough that the engine won't stall, then ramp it up gradually to full speed or wherever you plan to operate it. I run my rotary cutter anywhere from 2000 to 2400 engine rpm. I have an L3400 DT (gear drive). I suspect your PTO 540 on the L3700 equates to about 2350 engine rpm?

Not sure if the HST model has a foot throttle or not, if it does I'd recommend using it to get the mower turning. The hand throttle is a bit clumsy in comparison, but works ok once you're rolling along.

As to whether you have a problem (defect) or not, it's possible. It's hard to tell without actually hearing or feeling it, the dealer may be your best resource for peace of mind. Protect that warranty just in case you need it !

My 2 cents,

Sean

 

[e30racer]

I appreciate everyone's inputs. It sounds like the noise is normal but I'll probably take it to my dealer and have it checked out this winter while the tractor is still under warrenty.

This forum is going to be a valuable tool and a real benefit to me as a Kubota owner. Thanks to everyone who participates here!

Steven

 

[johnrex62]

I am away from my manual until Friday, but if I recall correctly it states to utilize the clutch when engaging the PTO. It recommends to engage the clutch quickly and disengage slowly.

When I have forgotten to slow things down and have engaged the PTO at a high engine rpm, the clutch technique allows the PTO to spin up with a similar sounds as I hear when increasing the engine speed after fully releasing the clutch. I don't think there is any difference in PTO load shock, but rather I might be putting more wear on the clutch if anything. Being new to tractors I had not thought much about it before. Glad to be getting some new perspectives before I break anything.

 

[Larry Caldwell]

The owners manual says to "Engage the PTO at reduced engine speed to avoid shock loads to the PTO". It does not define what "reduced" is so the wording definitely leaves some room for interpretation.

BTW, I know the noise is not coming from my rotary mower blades or gear box. The noise definitely emanates from below the drivers seat somewhere in the driveline.

Could anyone with a later model L3400 or L3700 that either does or has engaged their PTO at idle speed tell me if they get the same clatter/rattle/knock that smoothes out at RPM's increase?

thanks,
Steven

There's something wrong with your tractor.

 

[InThePines]

I have a new L3700 and have the same sounds at low RPM that go away as I increase the RPM. Dealer said that was normal. We probably have a year to figure out if it is a problem or not.

 

[ccsial]

My L3400 will rattle a little bit at idle. The rattle goes away when I disengage the clutch. I believe the rattle is the HST pump. It has always done this and has 270 trouble free hours.

Now as far as the PTO goes, I engage it at idle with a 6 foot finish mower and slowly let the clutch out. Then I gradually speed up to PTO RPM. There are no rattles during this process except the one that is always there from the HST pump if the PTO is on or off.

If I disengage the clutch there is a loud rattle from the OR clutch. This is why I disengage the clutch and PTO at the same instant.

I wonder if the L3400 and L3700 use the same PTO clutch setup. I have not even seen an L3700 yet. They are widening the highway by my dealer so I have have been avoiding stopping by as I used to do. That's probably saving me money.

 

[e30racer]

Yesterday evening I engaged the PTO with RPM's set at 1300 and there was absolutely no noise at all.

 

[TripleR]

Yesterday evening I engaged the PTO with RPM's set at 1300 and there was absolutely no noise at all.

That is about what I engage mine at. I see absolutely no reason to engage at idle. I have been driving tractors for well over fifty years and have a couple over fifty years old and have never broken or worn anything out operating the way I do. These are tractors built for work.

 

[DiezNutz]

60' Land Pride rotary mower... engage the PTO at idle RPM (800)

I think you've figured out already that the situation described is "normal" for trying to spin up an overdriven 5' blade at idle. Ever owned a riding mower, try to engage the deck at idle? If you didn't stall it, didn't it at least try to shake itself apart? Same thing. Likely the rattling/knocking you heard was driveline slack being jerked back & forth by the cutter. If you could hear all of the slop in your car's transmission in a high gear at idle with its wheels off the ground, it would probably scare you.

~1300 sounds like it works and has the consensus of most readers, so go with that. :thumbsup:

... and the blades stop flapping around and settle into their extended position.

flapping? extending?
I'm thinking you might need some heavier blades, or at least ones not made of rubber.

 

[e30racer]

I think you've figured out already that the situation described is "normal"

I have definitely reached the conclusion that everything seems to be normal. I've talked to the service dept at 4 different dealers and have been told that "they all do that". Although when I asked why, only 1 of the 4 provided the same explanation that Chilly and Diez gave (and which I am convinced is the correct explanation).

I did try engaging at 1100rpm last night and everything was quiet and smooth there also. Again, I appreciate everyone's input.

Steven