My L4740 with 180hrs has a problem, the PTO runs all the time, it will stop with the clutch. I split the tractor, removed the clutch pack, two disc are welded solid together,and there are a few others worn paper thin, I can see marks indicating heat. The only PTO attachment I have is a three point spreader I use when plowing snow. I've order replacement parts. my question, is this a common problem, any idea why this happened. I don't run the spreader at PTO speed because it throw's the cinders to far.
Need Advice on L4740 HST PTO Problem
- Thread starter Kubota 2007
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Is this a Dash 1,2 or 3 model? Dash 3, as in L4740-3 have a yellow electronic rotary switch to engage/disengage PTO. The others have a traditional lever.
I believe there are some differences between the models that might help diagnose your problem.
Judging by your light duty use it sounds like there is a problem with the clutch pack clamping force allowing clutches to slip. Might want to determine root cause before the new clutches fail.
I believe there are some differences between the models that might help diagnose your problem.
Judging by your light duty use it sounds like there is a problem with the clutch pack clamping force allowing clutches to slip. Might want to determine root cause before the new clutches fail.
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I'll look at mine later to see what -# I have. 505 hours and no PTO or clutch problems although I did blow a PTO shaft last week. That was after the tiller found a buried piece of a trailer axle. My neighbor did say 3 point implements should be raised in turns if that helps.
L4740D 50218. What's the difference between a D and a -1,2,3? Mines an HST so I'm not sure why the D is there.
I really don't know all the differences between the dash numbers (revisions) as I've never found a source quantifying the differences.
The dash # is not on the metal Model/SN tag. So your model is L4740D just like mine. On the left side of the plastic dash surround there is an adhesive tag that has the dash # published, assuming the tag is still present and they put them in the same location.
Having said this, there is a difference between how the -1 & -2 models engage the PTO versus the -3 models. The earlier versions use a traditional yellow lever to engage, while the -3 models use a plastic rotary switch. It looks like the -3 also has some type of valve on the side of the case to engage/disengage PTO clutches that uses hydraulic pressure.
This is only an educated guess on my end, but I believe the SN's for dash -3 start above 7xxxxx.
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North Idaho Wolfman
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Mine is a L4740-3, I did some looking yesterday, seems on the -3 models you must always raise throttle to PTO (540) when using PTO. Most implements operate at 540rpm, but two of the implements I have don't, using anything less the 540 PTO rpm's will cause overheating of the clutch plates caused by slippage, the applied servo isn't getting the correct pressure
allowing heat and slippage. I went through the owners manual, no where does it indicate you must run at 540rpm, looks like I'm going sell my post hole digger, or maybe buy a truck load of shear pins.
After a fair amount of use, 400 +/- PTO is the best for my tiller/tractor. Sure, I go slower but everything stays cooler. Try taking small bites with the augur.
Edit, mines a - 1 or 2, traditional handle.
Edit, mines a - 1 or 2, traditional handle.
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Where did you get this info from? Is the servo controlled by engine RPM directly or by an electrical signal (varying voltage) from the computer that determines PTO clamp pressure?
If an electrical signal is used for supply pressure perhaps it can be faked out by supply full voltage (whatever it might be), so lesser RPM's can be used safely.
I'm wondering if something is wrong with the OP's servo that helped cause this failure. Not saying RPM's didn't contribute based on your comments, but is there something else contributing to the clutches wearing so quickly. I'm guessing there are a number of people out there running under stated RPM with PTO equipment engaged and haven't experienced this problem.
The servo is controlled by pilot pressure from pressure reducing valve, there should by 340-360psi at full throttle, In the clutch pack there is a large coil spring that when hyd pressure is removed, this spring releases the clutches.Apply pilot pressure to the servo, it must compress the spring and hold the clutch pack together to prevent slippage. There is a 12volt solenoid valve that is either open or closed to supply pressure to the servo. Talked to a Kubota Tech he stated it is a common problem, also running at low rpm's will overheat the hydro system.
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Asked a service person at my local (very popular) Kubota dealer about the need to run at 540 PTO RPMs on newer tractors with the electronic controlled PTO solenoid to maintain line pressure to the clutch pack. They said no. Pressure might be slightly reduced at idle, but anything above 1500 rpms should supply full pressure to the clutches. Also asked if they PWM the solenoid during clutch engagement to allow for some slippage during initial engagement and he said he didn't know. So who to believe??? I'm not disagreeing with you, just stating what another dealership stated as I too like to run below 540 PTO rpms if it is not needed.
It also looks like there is an o-ring on the pipe that engages with the PTO solenoid. Perhaps if this is missing or damaged could result in low clutch pack pressure.
In researching the WSM there is a section about testing the PTO pressure at the solenoid valve. There is a 1/8 pipe port for this purpose. It states to test pressure at full engine speed. Pressure should be between 363 and 413 psi. If out of range, adjust regulator valve. See photo below.
Did they confirm your pressure is within specifications?
Perhaps a bit more research is needed to better understand the operating requirements. Does anyone have a pressure gauge and appropriate fittings to plot engine rpms with PTO clutch pressure?
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