M series hydraulic shuttle rocking back and forth in neutral

[rScotty]

Rancher,

I would say there is a leak at the shuttle input shaft carrier / sealing rings or the shuttle valve itself that is alternately leaking between the forward and reverse packs. I would have thought this would occur with hot oil, moreso than cold oil.

If the machine wants to move F/R cyclically in neutral, my thought is a leak and it should be taken to the dealer, put gauges in all three (F/N/R) ports at the same time and the pressure observed. You should never have pressure in forward and reverse without some input by the operator.YC

Rancher,
This is an idea from way out in left field.... but hear me out. If it was my tractor I'd be tempted to try a different hydraulic fluid from the SUDT. One of the things that I noticed at 200 hrs when I changed to SUDT on the M59 was that it noticibly eased the shifting between ranges. I had heard that might be the case, and hoping to loosen up the range shifting was one of the reasons for changing. It worked. The other reason for changing was a sort of archaic belief that something like SUDT that costs more does so because it is better. My younger friends think that's not being very logical.... but being an old guy I tell them that equating cost with value is a generational thing.

But as I changed the oil, I noticed SUDT also had an odd characteristic in that it foams noticibly more than whatever hydraulic fluid that Kubota had in there originally. Also it "felt" less slippery between my gloved fingers. The SUDT also forms lots of long-lasting entrained bubbles in the fluid when the oil is cold. Perhaps Kubota knows what it is doing with these fluids, but I'm an old engineer and have worked with fluid flow all my life. There might be some special purpose here I'm not knowledgeable about, but in general, those characteristics are a big no/no for hydraulic oils.

So....if it were me I'd be tempted to change to one of the JD or Ford hydraulic oils and give it a test for a few months. If possible I'd look for a hydraulic oil offering slightly more viscosity, higher lubricity, and a lot more resistance to foaming.
rScotty - M59

 

[Country1]

OP, did you find a solution to your problem?

 

[prophet455]

Mine was never resolved. I am not up for them tearing into the tractor without any ideas. The lower the gear, the harder the rocking. It is a forceful jerking not a gentle oscillating. Within 20 minutes of warm up it stops. Summertime it has no symptoms; at 40 degrees or so and lower it rocks.

 

[rScotty]

Mine was never resolved. I am not up for them tearing into the tractor without any ideas. The lower the gear, the harder the rocking. It is a forceful jerking not a gentle oscillating. Within 20 minutes of warm up it stops. Summertime it has no symptoms; at 40 degrees or so and lower it rocks.

Don't blame you for not wanting them to do exploratory mechanical work. What hydraulic oil are you using? Is it also the SUDT that Rancher has in his?
rScotty

 

[prophet455]

Did rancher ever get this fixed. Mine has never changed. It still does it in cold weather. Same as his. SUDT oil in it now- not entirely sure if UDT and SUDT from factory. The higher the gear the less violent the oscilating- implying its drag that does not have torque to hold in higher gears. At true idle it is not as noticable - I dont warn it up at idle. Around 1200 to 1700 is the areas it gets the maddest. Right now its summer obviously so no issue but this winter it was a rude reminder there is some concern when its warming up for work- it may decide to latch in solid and drive over me or the garage door.