2018 Kubota RTV-X1140 HST Failure and Rebuild with Pics

[sparkks]

Details:
2018 Kubota RTV-X1140
1225 Hrs 8005 miles

Symptoms:
In drive ranges or reverse shuddering on takeoff and low power transfer. Would not go up small inclines and had overall poor transmission performance.

Process: Changed suction rubber hose and filters symptom persisted.
Charge pressure 35psi
Traveling Side High Pressure 1500-1700psi
Attached are my initial findings I have a transmission shop for Automotive and Trucks. I will be taking this unit to the shop for the full tear down and rebuild due to having the tools and parts washers etc in house.

This is a part defect failure on the piston all other pistons on the pump are universally worn and unit doesn’t look to have any other critical wear yet. Full tear down will provide more light on the situation. Thanks for looking and input/information is welcome. Aloha

 

[bordercollie]

Interesting. Thank you for the great pictures and information .

 

[sparkks]

Interesting. Thank you for the great pictures and information .

No problem! I will have more coming with the tear down and the reassembly on this unit. To be honest I didn’t expect the damage to be this severe. Considering the machine still moved and would engage forward and reverse.

 

[aurthuritis]

very good info and pics. thanks for the pressure specs before tear down and description of symptoms. i wonder if the metal in the valves are soft? can you supply detail on lubrication specs and intervals? and a description of how it was used or service life?

 

[sparkks]

very good info and pics. thanks for the pressure specs before tear down and description of symptoms. i wonder if the metal in the valves are soft? can you supply detail on lubrication specs and intervals? and a description of how it was used or service life?

It was a piston on the high pressure pump that failed. I don’t have a way of testing the hardness. I’m wondering how thick the dome on the piston should be but Kubota doesn’t offer that spec in their WSM. Possible it started as a pinhole and at 3600+ psi it blew the top off. I found big chunks of the dome in the unit.

I can’t speak on maintenance or service use. I picked the RTV up from Herc Rentals as an inoperable machine. It had oem filters throughout with a date and hour that was well within the service period.

What I did notice in the gearbox was a lot of micro metal in the fluid almost had a greyish color and metal fine material on the magnet with no chunks or shavings. I doubt the gearbox fluid was ever changed judging by the condition of the fluid/magnet and the drain plugs looked to have never been touched.

 

[aurthuritis]

isn't the gear box and hst the same oil supply? thanks for filling in the info..... i would say lack of or improper lubrication i don't see any singes of heat.

 

[sparkks]

isn't the gear box and hst the same oil supply? thanks for filling in the info..... i would say lack of or improper lubrication i don't see any singes of heat.

No it is def not the same oil supply between the gearbox and the HST.

HST shares the power steering and bed lift cylinders etc via the hydraulic tank under the passenger seat.

 

[BiffNH]

isn't the gear box and hst the same oil supply? thanks for filling in the info..... i would say lack of or improper lubrication i don't see any singes of heat.

It is my understanding that the transmission (gear box) is lubricated with its own SUDT2 and the HST is lubricated via the hydraulic fluid (also SUDT2) in the reservoir under the passenger seat. It is the same fluid that is used in the power steering and hydraulic lift of the dump bed. This reservoir is so large because it is part of the all three systems and driving the transmission requires a lot of fluid and it needs so much to allow for cooling otherwise it would get way too hot.

 

[sparkks]

It is my understanding that the transmission (gear box) is lubricated with its own SUDT2 and the HST is lubricated via the hydraulic fluid (also SUDT2) in the reservoir under the passenger seat. It is the same fluid that is used in the power steering and hydraulic lift of the dump bed. This reservoir is so large because it is part of the all three systems and driving the transmission requires a lot of fluid and it needs so much to allow for cooling otherwise it would get way too hot.

Yes. I believe that’s why you see so much issues with low fluid levels in the tank. People service the HST check the gearbox dipstick and it’s still full and ride on. Also seems like the gearbox sheds some serious micro metal as it breaks in. Don’t think Kubota wanted that getting in the Hydro circuit.