L5740HST Drivetrain Slipping

   / L5740HST Drivetrain Slipping #11  
So the techs finally lifted the cab and split the tractor to discover this mess in the hydro drive. I see what parts were making the grinding noise now. One of the pistons in the hydro motor broke loose and helped chew up the others with the brass filings.
First parts estimate (plus the 30 hrs shop time @ $130) was $8k for a complete new hydrostatic. Once they disassembled, they revised it to $1700 for the parallel motors and $1700 for a new pump. Techs stated they rarely have ever seen a hydro failure, but for me with just under 300 hrs use I'm sure not impressed having to deal with it.
I guess its a lesson for me anyways, that if I cannot come close to using the warranty hours on a machine I sure will never consider buying a new one to include it.

View attachment 528631View attachment 528630

Completely unacceptable! Especially at 300 hours. Clearly pump had a defect when it was made leading to failure. I would raise h$ll over this with Kubota.
 
   / L5740HST Drivetrain Slipping
  • Thread Starter
#12  
I think it is a 2008 machine. Don't remember the warranty details from back then.
 
   / L5740HST Drivetrain Slipping #13  
I have a few bags of similar hydro piston around as souvenirs all resulting from low oil viscosity. Our problem was having released for production a machine that did not meet our hydraulic cooling requirement and in Middle East heat, oil viscosity became so low piston slippers started melting down. It was surprising how long the machines would run before one piston slipper would completely fail and the machine would stop.
 
   / L5740HST Drivetrain Slipping
  • Thread Starter
#14  
Thks for the info. I don't have my record book now to know exactly when I did the first hydraulic change, but It was replaced with the super UDT and a factory filter. This summer I used my 8 ft disc in high 80 heat for an afternoon, while the failure occurred in 60 degree temps in Oct.
 
   / L5740HST Drivetrain Slipping #15  
Thks for the info. I don't have my record book now to know exactly when I did the first hydraulic change, but It was replaced with the super UDT and a factory filter. This summer I used my 8 ft disc in high 80 heat for an afternoon, while the failure occurred in 60 degree temps in Oct.

Heck even if you did no maintenance... it shouldn’t fail at only 300 hours!
 
   / L5740HST Drivetrain Slipping #16  
Any chance of pictures of more parts? The most deformed slipper looks like something else was chewing on it as it went around. If it was an overheating situation seems like there would be some scorching or discoloration? The charge pump body (in the background) still looks decent. Failed Kubota (Kayaba?) hydrostats are rare to see in the flesh. You must want to get it running again asap - but it would be great to preserve the evidence of the wreckage for forensic study.
 
   / L5740HST Drivetrain Slipping #17  
If it was an overheating situation seems like there would be some scorching
or discoloration?

It looks like the slippers have worn down quite a bit. Pix of the valve plates would be nice to see as well.

Overheating the fluid can sure destroy an HST, but that one exploded slipper sure points toward a defect.

(Thx for posting pix, GARF.)
 
   / L5740HST Drivetrain Slipping #18  
It may have just been a defective part. It happens. I would think if it was bad oil then all of them would look similar. I guess it's possible something floating around in the oil got stuck on the face and damaged it. I doubt you'll get much help if it's a 2008 even though the hours are low.
 
   / L5740HST Drivetrain Slipping #19  
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.
 
   / L5740HST Drivetrain Slipping #20  
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.

Great information!! I hope OP reads this.
 
 
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