L2900 GST Shifting Problem

[SPYDERLK]

Hi. I have several Kubotas - none particularly modern - but all working fine until just recently. Then the ~ 1990's vintage L2900 I have had for 10 yrs had a circlip come loose inside that made it so that the PTO could not be disengaged. It is a known problem on this model. Kubota has an upgraded part and the dealer has spit the tractor put it in and fixed it. In the process they caused another problem which will severely hamper the tractors utility and they dont seem to be able to correct it.

The GST transmission no longer behaves correctly. - Im guessing this from symptoms ... but, when shifting it appears the auto hydraulic clutching and gear change still happens promptly as it should, but the clutch release to resume drive in the next gear is now badly delayed. The delay is so great that the tractor is liable to coast to a halt with every shift. The shop knows it is hydraulic related and happened there but doesnt seem to know how to trouble shoot the shift valving and get it back right. Worse, they have little faith in Kubota Technical Reps due to prior experience. Even worse, that might be warranted.?

Im sorta stuck here. I believe the senior mechanic is pretty good but not well enough experienced in this GST system. Does anybody here have some deep experience I could pass on to help resolve this issue?
Thanks!

 

[Dman1981]

Broken sealing rings believe they were not Teflon if you did not grease them up good to keep 'em shrunk dow you could clip it

 

[SPYDERLK]

Broken sealing rings believe they were not Teflon if you did not grease them up good to keep 'em shrunk dow you could clip it

Got it. Thanks for the reply. I went to the dealer today. The senior mechanic, Warren, had adjusted the low pass valve to increase shift speed, and then left. He told them that it was operating correctly. Maybe it is now - I didnt test drive it because it was raining and pertinent contact people were not present to deal with in any case.

The problem to me is why would the perfectly operating main drive transmission suddenly need adjustment after repair of the PTO engagement fault? A different mechanic did the PTO repair and his words after reassembly were "somethings not right". This was more than a month ago. I went and test drove it on the lot and the mechanics judgement was correct. The something was the shifting and they needed to find the errant condition and put it back right. I dont know what further actions they took while I left the degraded tractor there but the condition remained present without noticeable change as of last week.

Perhaps it will operate better now, after the adjustment, but that smacks of a (possible/probable?) end run around a root cause. While I was there today I looked at the valve block that controls the shift action sequence. It bolts to the left side of the transmission case. It was removed during the tractor spit repairing the PTO. Im thinking this valve block mates with flow paths through the casing interface to control the shift sequence actions.

Is this mating surface where those sealing rings do their job? It makes sense from my conception that a pinched seal at a flow duct could compromise a shift function by flow obstruction and maybe even by (hidden) leakage of some control fluid inward. I wonder if they verified that such a thing was not at the root of the problem. Any recommendations?
... I will update after I test drive it.

 

[Dman1981]

I can tell my eyesight sucks and spelling lmao

 

[SPYDERLK]

I can tell my eyesight sucks and spelling lmao

Im sorry. I hope you will be able to cope using your mental powers, experience, and imagination.

We, both my wife and I, test drove the tractor. The degraded transmission operation stemming from some unknown Murphy attack during dealer reassembly is still identically present. We have initiated a case with Kubota to bring in a Technical Representative with suitable knowledge to pinpoint and guide correction of the problem. The tractor has been at the shop for 10 weeks at this point.

 

[rbargeron]

I'd suggest posting about this GST issue on Orange Tractor Talks. One of the moderators there is a great resource on GST internals.

 

[SPYDERLK]

I'd suggest posting about this GST issue on Orange Tractor Talks. One of the moderators there is a great resource on GST internals.

Thanks! I may look there to see if the issue is discussed. -- The answer though is that there is nothing at all wrong with my tractor other than that the shop changed the fluid, refilling with UTD after the split. When cool, ~40F, this fluid is thick enough to delay shifting drastically. After a good warmup, nearly impossible to achieve in the dealer lot, the tractor shifts normally. I bought the tractor used and never had occasion to change whatever fluid it came with. It must have been SUDT or the like.
I am quite disillusioned with the talent at the dealer and at Kubota corporate. NONE took the cue and tried or advised SUDT even when I asked if that could be it. Adamant ignorance is very discouraging.

 

[rbargeron]

SUDT (or UDT before that) is quite low-viscosity high-priced fluid. If there's a viscosity problem, its more likely that the fluid put in was not SUDT but a cheaper oil of some kind ?

 

[SPYDERLK]

SUDT (or UDT before that) is quite low-viscosity high-priced fluid. If there's a viscosity problem, its more likely that the fluid put in was not SUDT but a cheaper oil of some kind ?

The work was done at a long established Kubota dealer. They said they used Kubota UTD acquired from Kubota in bulk/drum quantity. I can only take their word.

Back when I started becoming aware of the nuances of lubricating and working oils in tractor transmission/hydraulic/brake use I learned that the goto designation was UDT, UniversalDynamicTractor oil. This was the oil compatible with both hydraulics and the extreme pressure situation of gear drive. Then there were the "SUPER" ones. Kub actually called theirs that - SUDT and later SUDT-2. Other suppliers made "super" ones too, to match the need for excellent flow and protection from cold to full heated conditions of use. The gist was providing a high ViscosityIndex oil, starting pretty thin, and getting only a little thinner with heat. The synthetic fluids can provide this high VI. They cost more. -- In some cases the benefit outweighs the cost.

Below is a video I just ran across while looking to compare the UDTs vs the Super variety. Around 3-1/2 minutes shows a side by side cold flow demo of both. I have bought some Lucas Synthetic UDT to compare to Kub SUDT-2 since the Lucas synthetic was not tested in the video. The Lucas only costs 70% of $UDT-2.

 

[JTDude]

Hi. I have several Kubotas - none particularly modern - but all working fine until just recently. Then the ~ 1990's vintage L2900 I have had for 10 yrs had a circlip come loose inside that made it so that the PTO could not be disengaged. It is a known problem on this model. Kubota has an upgraded part and the dealer has spit the tractor put it in and fixed it. In the process they caused another problem which will severely hamper the tractors utility and they dont seem to be able to correct it.

The GST transmission no longer behaves correctly. - Im guessing this from symptoms ... but, when shifting it appears the auto hydraulic clutching and gear change still happens promptly as it should, but the clutch release to resume drive in the next gear is now badly delayed. The delay is so great that the tractor is liable to coast to a halt with every shift. The shop knows it is hydraulic related and happened there but doesnt seem to know how to trouble shoot the shift valving and get it back right. Worse, they have little faith in Kubota Technical Reps due to prior experience. Even worse, that might be warranted.?

Im sorta stuck here. I believe the senior mechanic is pretty good but not well enough experienced in this GST system. Does anybody here have some deep experience I could pass on to help resolve this issue?
Thanks!

Might I ask how much your dealer charged to fix the rear PTO disengagement issue? Mine just failed and I think I have the same problem internally. Could it be a DIY repair?