Kubota HST Issues

[Sockwell]

Good morning. I'm a prodigal son that is trying to come back to the fold. I am having an issue with a Kubota and need the help of the guys here. I have a 2013 L5740 HSTC-3. The tractor has been serviced per the owner's manual. It now has about 775 hours. About a year ago, I started having issues with the transmission. When it has been in use for several hours (4-to-5 hours), something happens with the oil flow in the transmission. The engine continues to run fine. The tractor may have a few mild surges and will then forward motion will slow considerably. The problem continues to get worse until forward motion on even level ground requires feathering the throttle and will eventually lead to having to shift down to Low range and creep along.

When the tractor is then parked and allowed to cool, the process starts over: It runs great for a while, then gets to the point where it struggles to move. Where do I need to start to find the problem? This problem spans a change of hydraulic and transmission filters and the fluid is within the correct operating level. Only Kubota filters and Super UDT have been used. A small amount of John Deere hydraulic oil dye was added to the oil years ago to help see the oil level on the dipstick.

To this point, I've tolerated the issue by using a second tractor to cover the need. However, I'd like to get this one running to have a cab. Any and all help is appreciated.

 

[Harry in Ky]

While you have a hydrostatic transmission you also have a dry clutch ahead of it. Your description of events could very well be caused by that clutch slipping under certain conditions. Is there any free play in the pedal? That would be the first thing to check.