Kubota L4740 PTO, Check the pressure

[Kubota 2007]

Kubota L4740 PTO will not shut off, tractor has 170 hrs, I split tractor to remove PTO clutch pack, clutch disc and steel plates welded together, clutch pack shows heat present. Replaced clutch pack,seals gaskets,filters and fluid. Kubota repair manual describe's checking and adjusting Pressure Reducing Valve. I purchased a digital pressure gauge, specs show PTO engaged, Eng, @ Max speed, you should have 334 - 362psi, I have 280psi. I only use this tractor for plowing snow and the PTO for spreading cinders from a HERD spreader, the PTO clutch has been slipping from day one, using the PTO spreader, I wouldn't notice any slippage until as it did build up heat and weld the disc together. I have replaced all parts and adjusted the Pressure Reducing Valve to 350psi, and have over $1600.00 in bills and many hours labor for a problem that I had no control over.

 

[moship]

Sorry to hear about your problems and appreciate you posting what your PTO pressure is. Do you think it was 280 psi prior to the failure?

After setting the pressure to 350 psi did you by chance test the pressures at other RPMs?

After reading about this problem with the PTO earlier, I asked the service manager about the pressure and he implied that once over idle, say 1,500 rpms the pressure should be sufficient. In reality he didn't know what the engine RPM vs pressure relationship looks like. I'd hate to have to run at max rated rpms simply to have sufficient pressure to keep the PTO clutch pack engaged.

What fitting is needed to check the pressure? I'm hoping it's 1/4" NPT as I already have it. What do you think would happen if the pressure was above their recommendations?

Your advice hold true for all GL40-3 and all the new GL60's with the rotary PTO engagement switch.

 

[Kubota 2007]

I did check the pressure at different RPM's, anything under 2000rpm and the pressure drops under 300psi, if that is sufficient to engage the clutch's who knows. I do know that the 280psi my tractor had it took two years of use to overheat and weld the disc together the other clutch disc were worn thin, with only 170 hrs on tractor and possibly 25 hrs of PTO use I wouldn't want to take another chance, not a real bad job replacing it but with parts fluid and filters I have $1600 out. The seal rings on the clutch pack wouldn't take much pressure, and if they failed it is the same job to replace.

 

[moship]

Thanks for the reply.

Do you remember the testport threads? I壇 like to test mine but want to be certain to have everything before starting.

Failure of your type is obviously created by a factory issue and agree they should have made this right even if out of warranty.

I also believe they should have a big warning note in the manual and label near the engagement button stating what the minimum rpms.

 

[Kubota 2007]

Sorry I forgot, 1/8"np. I contacted Kubota customer complaints, they sent me a note saying, if your tractor has been fix by anyone other than a Kubota dealership, you have no claim with Kubota. But I'm not done, I'm going to the next level.

 

[moship]

Thanks for the thread size and good luck as you move this up the chain.

What is the OD & ID of the clutches?

Any chance a seal was damaged from the plant causing the clutch pack pressure to be even lower?

 

[moship]

Where did you get the pressure specifications? I see a different pressure specified... 363-413 psi vs. what you reference, 334 - 362psi

See attachment.

Added in edit...
Further research indicates there are different set pressures for the PTO depending on if HST or not. The HST is set to 363-413 psi.

 

[Kubota 2007]

Thanks for the thread size and good luck as you move this up the chain.

What is the OD & ID of the clutches?

Any chance a seal was damaged from the plant causing the clutch pack pressure to be even lower?

Seals look great, I'll get back to you on Clutch measurements.

 

[Kubota 2007]

Where did you get the pressure specifications? I see a different pressure specified... 363-413 psi vs. what you reference, 334 - 362psi

See attachment.

Added in edit...
Further research indicates there are different set pressures for the PTO depending on if HST or not. The HST is set to 363-413 psi.

I purchased the service manual when I received the tractor, the specs you have are they for a L4740-3..... You have me wondering now about the pressure, I have mine set at 350psi, but when moving the tractor (HST) the pressure drops. Does your manual have the year of publication?

 

[moship]

Year of manual is Feb 2015 and it is for all newer GL40's.

According to the Kubota's parts website it looks like L4740-3 and smaller use 6 clutches/steels in the clutch pack, while the L5240-3 and larger use 7. I'm wondering if you could have used the 7 clutch/steel clutch pack to get more torque capability.

Do you think the HST requires higher pressure to compensate for the lower pressure when moving? How much does it drop when moving and does it ever recover?

What is the published date of your manual?