Kubota Grand L3940 PTO questions

[beppington]

Kubota says about my Grand L3940's PTO:

1 Speed Rear Live - Hyd. Independent
540 rpm @ 2550 Eng. rpm
Electric over Hydraulic PTO Switch (-3 only)

The manual says: "To avoid shock loads to the PTO, reduce engine speed when engaging the PTO, then open the throttle to the recommended speed." ... which I've done every time since new.

Questions:

1) When the tractor is completely shut down & the PTO is off, I can only turn the PTO shaft a little ways in each direction, like maybe a half a turn worth of free play. Why is this? Does my PTO have a brake?

2) Should I also reduce engine speed when disengaging the PTO?

Thank you all, as always ...

 

[TripleR]

There is a rather lengthy thread on here with a lot of good information. Prior to reading the thread, I did not reduce RPM's when disengaging as I was use to operating older type tractors with different systems than on the L Series and other more modern tractors.

http://www.tractorbynet.com/forums/...g/177989-disengage-power-take-off-before.html

 

[JOHNINMA]

On my L3540 I depress the clutch pedal while the tractor is idling then turn on the pto and slowly let the clutch back out totally eliminating any shock load whatsoever. My tractor manual just says to engage the pto at idle, but I found this extra step allows me to slowly bring the pto up to speed with zero shock. I reverse these steps to disengage the pto as well. Its most likely overkill, but it makes me feel better.

 

[Chilly807]

As to the first question.. I have no idea.

The second one is easier. My feelings on it are this: with a "high-inertia" implement, like a rotary cutter for example, it's best to engage and disengage at a low speed whenever possible to both preserve the clutch life and to slow the implement down.

The engine is the best brake for slowing down, although your PTO may ratchet if you close the throttle sharply. Mine just drags down the implement speed as the engine comes to idle.

Sean

 

[Gordon Gould]

There is a rather lengthy thread on here with a lot of good information. Prior to reading the thread, I did not reduce RPM's when disengaging as I was use to operating older type tractors with different systems than on the L Series and other more modern tractors.

http://www.tractorbynet.com/forums/...g/177989-disengage-power-take-off-before.html

Quite an interesting thread. But you have to read the whole thing before coming to any conclusions. Thanks for pointing it out. When it was originally posted I did not follow it to its end. But now after reading all of it I will power down before disengaging my independent pto.

 

[crazyal]

I've just err'd on the side of caution and always engaged or disengaged the PTO at idle with the clutch in unless it's an emergency then I just press the clutch in.

 

[beppington]

There is a rather lengthy thread on here with a lot of good information. Prior to reading the thread, I did not reduce RPM's when disengaging as I was use to operating older type tractors with different systems than on the L Series and other more modern tractors.

http://www.tractorbynet.com/forums/...g/177989-disengage-power-take-off-before.html

Well crud, I had actually read that thread & even posted in it: Stupid me!

radman1's post #4 answers both of my questions: It is best to idle down before shutting of the pto. Why? Because of the pto brake. Every modern day pto has a brake. Safety device to stop the pto faster than just "coasting" to a normal stop. When your coat is being wrapped into the pto shaft and your buddy shuts off the pto, you will be greatful for the pto brake. High speed rpm and lots of pto inertia, put more strain on the pto brake and it will wear out faster. My large ag tractors with pto brake can undergo a lot of braking with 1000 rpm ptos. I can actually push a button on my tractors to override the pto brake and allow the pto to coast to a stop.
Many times when mowing, I will idle down, disengage the pto and keep moving the tractor/mower into uncut grass, to help slow down the pto and prevent more wear on the brake.

and his post #5: Forgot to add, the pto brake is why you see the shaft of the pto stop very quickly even without a pto shaft attached. If you ever see a modern tractor take a long time to stop the pto from turning, the pto brake is probably worn out.

It makes sense I guess that the PTO brake stays on whenever my PTO switch is off ... And that's the reason I can't freely rotate my PTO shaft or implement when the tractor's off? I guess I'd need the PTO-brake override switch radman1 mentions in order to do that.

Oh well ... mystery solved.

 

[Chilly807]

Not necessarily... mine has no PTO brake and it's a 2009 model. Some different types have brakes, no question, mine doesn't have the over-running clutch either. I do believe yours has the over-running clutch, being an HST model, so you may be feeling the resistance from the ramps on the clutch.

My PTO is free to turn anytime it's not actually engaged. The only PTO brake I have is the engine compression, as it comes to idle it also slows down the PTO shaft (live PTO). If you press the clutch fully in while the implement is still turning, it's inertia lets it keep spinning, gradually slowing down as friction takes it's toll. A PTO panic stop with my tractor means not touching the clutch, instead bringing the throttle to idle and turning the engine switch off.

Part of the confusion stems from the mnay types of PTO systems out there across the brands and model lines. Kubota alone has at least two types if not more.

Your's is an independent hydraulic PTO. I think so anyway... if that's the case, when you press the button or pull the lever to engage the PTO, hydraulic pressure forces the clutch disc/pack into engagement, which in turn rotates the PTO output shaft. When you disengage the PTO, the hydraulic pressure is released and the shaft is no longer driven by the engine. There may well be a brake that's engaged when there's no hydraulic pressure applied to the PTO clutch. Similarly, if you lose hydraulic pressure for whatever reason (engine stall for example) the PTO will disengage as soon as the pressure is lost, and the brake (if there is one) will stop the implement.

The over-running clutch is there to prevent the implement from "driving" the tractor or damaging the HST on those models, or so I've been led to believe.

Clear as mud, right?

Sean

 

[kevinj]

Kubota says about my Grand L3940's PTO:

1 Speed Rear Live - Hyd. Independent
540 rpm @ 2550 Eng. rpm
Electric over Hydraulic PTO Switch (-3 only)

The manual says: "To avoid shock loads to the PTO, reduce engine speed when engaging the PTO, then open the throttle to the recommended speed." ... which I've done every time since new.

Questions:

1) When the tractor is completely shut down & the PTO is off, I can only turn the PTO shaft a little ways in each direction, like maybe a half a turn worth of free play. Why is this? Does my PTO have a brake?

2) Should I also reduce engine speed when disengaging the PTO?

Thank you all, as always ...

On my Grand L you can feather the PTO in softly, I still throttle down so as not to slip the PTO too much. Don't just slam the lever forward.

 

[beppington]

On my Grand L you can feather the PTO in softly, I still throttle down so as not to slip the PTO too much. Don't just slam the lever forward.

I have the little yellow knob you turn to the right for "on" (see below). It feels like a switch that can't be feathered ... just on or off. Maybe I'm wrong?

Yours must be a different year than my '10, if you have PTO "lever"?

(Ignore my un-plugged seat switch; I would "never" knowingly bypass a safety switch. Or would I?!? :confused2: ...:laughing