M series hydraulic shuttle rocking back and forth in neutral

[Chilly807]

I have no idea what's in the hydro shuttle mechanism, but it's like the shuttle valve has too much free play and "bounces" from one end of the neutral position to the other causing a slight movement either way at the end of each bounce.

Even if it's not under warranty I think it might be worth your while to talk to Kubota USA and tell them you have a safety concern. Neutral should be neutral.. period.

They might be willing to do a good-will (aka keep-your-mouth-shut) fix in your case.

Sean

 

[rScotty]

I
They might be willing to do a good-will (aka keep-your-mouth-shut) fix in your case.Sean

Wouldn't a "good-will fix" work out better if the owner told everyone about it? Am I missing something here?
rScotty

 

[Chilly807]

Wouldn't a "good-will fix" work out better if the owner told everyone about it? Am I missing something here?
rScotty

Just the way my mind works... they don't want an unhappy customer telling everyone about the "trouble they had with the Kubota", so they fix the issue he's having, they're under no obligation to do that but it's good business. I think the saying goes, "If you have no problems with it, a few people know, but if you DO have trouble, everyone knows."

Something like this could turn into a safety issue under the guidance of a "good" lawyer. There's obviously a problem with this tractor since they don't all do it.

Sean

 

[Tnbilly]

Checked the service manual, the only "not staying in neutral" in the troubleshooting guide listed only cable adjustment or replacements due to bending. PM me with an email and I'll send you the cable adjustment pages if you're interested.

Ron

 

[rancher93]

Kubota dealer's head mechanic finally got back to me. He says he has heard of this problem previously.

He said when the other tractor that exhibited this problem of rocking back and forth in neutral was disassembled, all was ok internally except for a very slightly warped clutch disc.

That's what he thinks is causing my problem. Why it only does this when cold he had no answer for.

His suggested solution: jam the parking brake on very hard so the rocking will not be apparent!

Perhaps it is time to contact technical support at Kubota.

 

[Yankee Clipper]

Rancher,

Does this happen only at cold start - first thing in the morning? Is it a function of temperature of the UDT?

Are you in an area that is below zero in the morning? Have you considered using Super UDT or like fluid with a pour point depressant (PPD)?

It may be the shuttle pack is dragging due to the oil hanging to the faces of the discs / plates and the tractor is trying to move. I heard of this years ago with Case IH Magnums in Canada in winter and it was solved with Hy Tran Plus (had a PPD to keep things moving) plus use of a transmission heater. But they only moved one direction.

Also to clarify, it tries to move both forward and reverse without you moving the shuttle handle?

 

[rancher93]

Only seems to happen when cold. Temperatures between 20 F and 40 F.

The tractor has always used SUDT fresh from the dealer.

It rocks forward 2 inches then rocks back 2 inches to the initial position. Then rocks forward 2 inches, then rocks back 2 inches. Repeatedly.

The motion is at about a one second rate, in other words about 50-60 times per minute.

The hydraulic shuttle lever is not touched and remains in neutral position.

 

[rScotty]

Only seems to happen when cold. Temperatures between 20 F and 40 F.

The hydraulic shuttle lever is not touched and remains in neutral position.

Initially didn't you write that it didn't do it with the hydraulic shuttle in neutral? Is this new behaviour?

"" and the rocking can be totally eliminated by placing the high/ low
(rabbit/turtle) selector in the middle of its range of travel (where neither high or low is selected).""

It would be nice if it were a warped clutch disk, but it doesn't sound like it explains enough of the symptoms. Does fully depressing the clutch change anything?
If the clutch is dragging enough to spin the mainshaft in the thick oil then some drive could be transferred to the wheels....but probably only in one direction. As for the alternating back and forth are you convinced that this is driving in both directions? Or is it driving in one and then rocking back? That would seem to help differentialte the problem between oil drag or hydraulic shuttle oscillation.

Even out of warranty, I'd get the problem formally on file with someone at the main Kubota warranty dept. Like a lot of big corps they do put effort into improving things, but I doubt that means that they always advertise an improvement to existing owners.
rScotty

 

[rbargeron]

Initially didn't you write that it didn't do it with the hydraulic shuttle in neutral? Is this new behaviour?

"" and the rocking can be totally eliminated by placing the high/ low
(rabbit/turtle) selector in the middle of its range of travel (where neither high or low is selected).""

It would be nice if it were a warped clutch disk, but it doesn't sound like it explains enough of the symptoms. Does fully depressing the clutch change anything?

Placing the (rabbit/turtle) lever in the middle puts the gear range selector in neutral - so no surprise it stops rocking then.

rancher93 - when the Kubota mechanic talked about finding a "very slightly warped clutch disc" - was it one of the many clutch discs in the shuttle ? In which case was it in the forward half or the reverse half? (There's a stack of discs in each). This is a head scratcher.

It's hard to imagine a mechanical reason for rocking in both directions, unless it's two warped shuttle discs. Hydraulic pressure somewhere might be oscillating - maybe a valve that's not in exact step with its linkage notches?

 

[Yankee Clipper]

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.

Again, get the dealer involved now.

Good luck!

YC