L5740HST Drivetrain Slipping

[MHarryE]

Here are 2 items from my hydraulic pump/motor failure analysis manual. As shown here and in my experience, a sticking piston will usually break the retainer plate and yours appears sound. Still it explains how to identify a sticking piston by scuffing, abrasion marks on the piston.

I can't find my collection of failed piston - my wife has a different opinion of art than me so she stored them away where I can't quickly find them. I know I've posted pictures on this site before for trouble shooting help.

Under the conditions you describe, there should not be a viscosity problem. Still I do not understand why Kubota does not have a hydraulic temperature warning on their tractors. Its not that they won't overheat - I've measured temperatures beyond hydraulic component supplier limits on both my M135GX and L5740 - Here in cool Northern Minnesota. M was due to a faulty valve that kept the system at continuous relief pressure. L was operator abuse - I worked it too hard in dirty conditions that partially plugged the oil cooler. Engine temp alert they have but equally expensive hydraulic system no monitor. I keep an I-R thermometer on each of my tractors.

 

[dfkrug]

Here are 2 items from my hydraulic pump/motor failure analysis manual.

Nice pix, MHE. Who writes that manual?

I have not heard the term "adhesive wear" before. It seems to mean the failure of the lubrication film.

I am also guilty of collecting failed components for show-and-tell.

 

[rbargeron]

..........I have not heard the term "adhesive wear" before. It seems to mean the failure of the lubrication film.....

It's another term for galling. When the lube film layer gets too thin high points on the surface grains start contacting and burnishing each other. The friction causes even more heat and pretty soon "pills" start rolling out of the surfaces. They quickly get bigger than the tiny clearance and it locks up. Hydrostatic drives need clean and perfect surface shapes and durable lube film thickness, else game over.

 

[garf658]

There is a known manufacturing issue with a serial number range of L40 HST transmissions. The tolerance between the HST piston and bores are to tight and will seize in the bore. The slipper will get hammered against the swashplate when it gets tight in the bore and either pull the slipper completely off the piston or hammer the face as has happened to yours. I had this failure occur when my tractor was within the warranty period. Make sure your dealer installs the most current parts or this could happen again. I would ask your dealer to contact kubota if they are not aware of this type of failure and proper repair solution. No problems with my HST since new parts were installed.

Thanks for the info. I'm getting home next week and certainly will ask them about this.

 

[moship]

Garf658, can you post the outcome of this issue. Curious what you found about "Known problem" lakeridge suggested.

 

[garf658]

Moship, sorry to say yours sounds very similar to mine.
The service manager said they knew of some change-ups back in the early model years and repaired as necessary if warranty applied. The final outcome on mine was a new hydro motor and pump, 30 hrs shop time. New parts are now all the updated ones.
Also want to send a shout-out to Edmonton Kubota for giving me a 10% discount on the parts and a discount on the hours. At least that was 10% more than Kubota offered for a $7k bill.

 

[moship]

Fortunately my tractor is ok, but another forum member might be having a similar problem.

Thanks for sharing the outcome dispite the pain of spending $7,000 to repair something that was very likely no fault of your own.

I trust it has been trouble free since the repair.

Reference to other link
http://www.tractorbynet.com/forums/kubota-owning-operating/390244-l5240-hst-chatter.html

 

[garf658]

Yeah, I was referring to Snoboy. Hopefully its a better diagnosis than mine.
As far as the trouble free part, it will not be seeing any use till Spring. Believe me I'll be working it every chance I get. The 3830 will be having an easy summer.