HELP!!! L4400HST PTO Clutch

[tallyho8]

I bought an L4400HST 24 months ago and think I have a PTO clutch problem. I push in my clutch pedal, put the PTO in gear, slowly let up on the clutch pedal and then raise the throttle. The 6' bush hog starts turning fast and will cut light grass.

When I go into thick grass, the driveshaft to the bush hog stops turning. I am thinking that the PTO clutch is worn out but can't believe that it could have happened so soon with so little light use. I always baby the clutch when engaging and disengaging the PTO and have done very little bush hogging with this tractor.

I only have 150 hours on it and maybe 40 of these are cutting grass. Mostly it is using the box blade, disc or front end loader. My last 2 tractors cut my heavy grass for over 10 years each without ever changing a clutch and the last one was just an 18hp Yanmar. No one has ever driven it but me and I baby my equipment.

Even though it is still under warranty, there is no warranty at all on a clutch disc and it must be very expensive to replace.

1. Is this a worn out PTO clutch or could it be something else?

2. If it is a worn out clutch, what could have made this new Kubota wear out a clutch so quick?

 

[johnrex62]

Why do you think it is the clutch? Wouldn't a bad clutch prevent you from engaging the PTO? It sounds like you are engaging the PTO without problem. Did I miss something?

It sounds more like a hydraulic issue rather than a clutch issue.

 

[dex3361]

I would check the clutch engagement lever that the cable operates. Do you have a parts manual for your machine? If not pm me.

 

[Gator6x4]

I would check the fluid level just to be on the safe side. It sounds like the shear pin or bolt has sheared. If the Rotary Cutter has a slip disc clutch this may be too loose. My money is on the shear pin or slip clutch on the Rotary Cutter.

 

[tallyho8]

Why do you think it is the clutch? Wouldn't a bad clutch prevent you from engaging the PTO?

I am not familiar with what kind of PTO clutch is in this Kubota. I know that a worn standard transmission clutch disc in a car or tractor will slip when it is under a load and I don't know if this PTO clutch operates under the same principle. Also, there may be a built-in slip clutch that is slipping too easily.

I would check the clutch engagement lever that the cable operates. Do you have a parts manual for your machine? If not pm me.

I checked and the cable is pulling the lever all the way up to the stop where it can't go any further.

 

[tallyho8]

I would check the fluid level just to be on the safe side. It sounds like the shear pin or bolt has sheared. If the Rotary Cutter has a slip disc clutch this may be too loose. My money is on the shear pin or slip clutch on the Rotary Cutter.

The fluid is full and the filter only has 94 hours on it.

The PTO shaft coming out of the rear of the tractor that connects to the PTO driveshaft going to the bush hog stops turning so it would not be a shear pin or slip clutch on the cutter.

 

[dstig1]

What RPM are you running at?

 

[tallyho8]

What RPM are you running at?

I was running at 2000 rpm. If the PTO shaft isn't turning at 2000 rpm, would running at a different rpm make it turn?

 

[dex3361]

I was running at 2000 rpm. If the PTO shaft isn't turning at 2000 rpm, would running at a different rpm make it turn?

No, the pto should work at all RPMs. Unless maybe the hydraulic pressure is right on the edge of operating the clutch pack and that little bit extra helps it operate.

 

[dex3361]

I have attached a PDF of the parts diagrams that relate to the L4400HST.

I would check the fluid levels since the PTO clutch is hydraulically operated.

I haven't really studied this all the way out but it looks to me like the PTO clutch is hydraulically engaged by the movement of the lever that operates the cable that attaches to the PTO clutch valve.

If the valve is not rotating all the way the it would not apply full pressure to the clutch pack.

Could be low hydraulic pressure going to the valve or through the valve.

The clutch pack could have a blown seal in the piston.

I might try to engage and disengage the PTO with the lever (fender mounted) back and forth without a load on the PTO in the hopes the piston or valve may be stuck.

If this doesn't help then I would go through the test procedure in the shop manual to see if you have the proper pressure going to the clutch pack.

Keep us posted.

 

[dstig1]

I was mostly curious if you were running it super low RPM and maybe were bogging it down that way. Doesn't sound like that is the issue...

 

[johnrex62]

The specs on the L4400 indicate the proper engine RPM for the PTO is 2600. I don't think running it at 2000 would prevent it from turning before it bogged the engine down, but you are not getting 540 at the PTO at 2000RPM.

 

[tallyho8]

Randall
Thank you for the pdf. I will save it for future reference.

I got in touch with my Kubota dealer today and he told me that it WAS covered by warranty and that my warranty ends in 5 days.

I loaded it up and rushed it over to the dealer and I will know something next week.

 

[dex3361]

Your welcome and keep us posted on the details.

 

[doall]

good luck. Hope its something easy.

 

[tallyho8]

After a week the dealer phoned me and said it was fixed. He said all they had to do was adjust the pto cable. I said that could not have been the problem because the cable moved the lever all the way to the stop, but they insisted that it was fixed.

I brought it home, hooked up the cutter, tried it out, and nope, not fixed, pto still slipping.

I brought it back to them the same day with the cutter on and they tried it in tall grass and saw how it was slipping and said they will fix it but I haven't heard from them yet.

 

[tallyho8]

I phoned the dealer today and they said they changed the oil and filters and that it "looked" like it was working ok. I asked if they cut any grass with it and they said they had no grass to cut so they couldn't test it.

I told them to put it on a pto dynamometer and test it and they said they don't have a dynamometer and that they have to send it to a little town 70 miles away to get it tested.

I wish I had brought it to the little town dealer instead of the big city dealer to get it fixed. Maybe they would know what to do. Now I have to wait another week for them to transport it to the other town to get it tested.

 

[tallyho8]

Update: I checked with the dealer today. They said my tractor failed the dynamometer test and was only getting about 25 hp to the pto.

They have to split the tractor and probably replace pto clutch discs and it will be about another week.

I sure hope that this is not a common fault with an L4400 because I only have about 40 hours on this pto and can't imagine why it failed so soon. I would hate to pay for this job if it wasn't under warranty.

 

[JC-jetro]

Update: I checked with the dealer today. They said my tractor failed the dynamometer test and was only getting about 25 hp to the pto.

They have to split the tractor and probably replace pto clutch discs and it will be about another week.

I sure hope that this is not a common fault with an L4400 because I only have about 40 hours on this pto and can't imagine why it failed so soon. I would hate to pay for this job if it wasn't under warranty.

Tally,

As the diagram clearly shows you have a hydraulic pto clutch. You do have one main clutch for the locomotion. You have two shafts, one solid and the the other one hollow, one for transmission and one for pto. The pto shaft is splined and is directly coupled to crankshaft/flywheel. Any time the engine is on the pto shaft is turning but not the pto final shaft. what couples the pto shaft to final pto shaft is a set of wet clutch disk. Now, if you engage the pto and the clutch pack is not compressed hard enough then you have slippage that even causes premature wear on clutch disk... not a good thing. just imagine you're going downhill and push the break pedal only 1/4 of it's full travel. Obviously, you can not stop because of not enough friction is caused. if you continue driving like that you will just burn off disk material against the rotor and things get hot. The coupling of PTO on some tractor is done electro hydraulically or mechanically. I think your pto clutch is slipping in your case and that's not good. it is either caused by incorrect adjustment or pto disk are worn out. The wet clutch pack should outlast a normal dry clutch, so there is good possibility of bad adjustment from the get go..I'll study the pto engagement or ask the dealer about it.

JC,


edit: I did go and took a look at the pto engagement cable. The cable operates a pto control valve (mechanical and not electro mechanical). I see adjustment there on the cable tension. I can not see the valve is two position or modulating, if the engagement cable does not fully open the valve then you can not get the flow pressure needed to press the pto clutch together all the way. if The valve is fully open thane you might not have the right hydraulic pressure to compress the wet disks together. two thing you need to know, one is if the valve fully opens and has no internal port restriction and secondly what pressure you have when the valve opens and if that pressure is within operating requirement of the pto clutch pack.

 

[tallyho8]

Thanks for your explanation JC. What I am really worried about is that they will replace the clutch discs but not repair what caused them to go bad in the first place and when they wear out again next year it will not be covered by warranty and will be a $4000 repair job.

And after my tractor being in this shop for over 3 weeks, I have absolutely no confidence in this dealer.