# Kabota L4150DT Hydraulic Shuttle "Slipping"



## gpsmatty (Dec 28, 2021)

Hi Guys,
I just picked the tractor up, PO had health issues, and it sat for five years until he passed away, and I purchased it from the estate. I changed the oil, flushed the fuel, and put a new battery in, and the tractor fired right up (huge relief). The 3 point lift works bucket lifts and has enough power to lift the front wheels of the tractor, but it won't go anywhere unless in the lowest gear, and that's only sometimes. The best way I can explain it is it feels like it's slipping. 

At this point, I feel like I've read everything there is to read on similar issues, and this:
https://www.justanswer.com/agricult...ta-hyd-shuttle-want-move-forward-reverse.html

That site sucks, and there is no resolution to his problem, but that's precisely what I am experiencing.

SO far I have messed with the linkage on the shuttle, switched it between the 3 different engagement settings, changed the hydraulic filter, checked fluid, and still same results. 

One thing I tested was having someone watch the PTO when I am in gear and it starts "slipping" and the PTO does not turn which leads me to believe its the main single disk clutch. The fact the hydraulics work great also leads me to believe its not a shuttle issue.

Looking for some input as this is my first tractor.


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## SidecarFlip (Mar 25, 2021)

If it's a hydraulic shuttle it has no dry clutch and the lock up pressure on the travelling clutch pack is insufficient. I suggest either acquiring a Workshop Manual or have a Kubota dealer diagnose the issue. Takes specialized tools to set the pack pressure. You might try www.kubotabooks.com for a download.
, but even with a Workshop Manual, I strongly suggest having a Kubota dealer diagnose and fix the issue.


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## SidecarFlip (Mar 25, 2021)

The hydraulics and the travelling and pto clutch packs have nothing to do with each other, other than the clutch packs get their clamping pressure from the hydraulic pump. It's an internal pack issue and you fiddling with it and not having the proper tolls will only aggrivate the issue.

I might add that continued slipping of the travelling pack will eventually destroy the clutch plates and render it useless.


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## gpsmatty (Dec 28, 2021)

SidecarFlip said:


> If it's a hydraulic shuttle it has no dry clutch and the lock up pressure on the travelling clutch pack is insufficient. I suggest either acquiring a Workshop Manual or have a Kubota dealer diagnose the issue. Takes specialized tools to set the pack pressure. You might try www.kubotabooks.com for a download.
> , but even with a Workshop Manual, I strongly suggest having a Kubota dealer diagnose and fix the issue.



I do have the workshop manual and this specific model does have a single disk dry clutch between the engine and transmission in conjunction with the clutch packs for the hydraulic shuttle. My point is that the PTO does not turn when the tractor is "slipping" not moving forward leading me to believe it's the single disk dry clutch between the transmission, because the clutch packs for the hydraulic shuttle have nothing to do with the PTO.


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## SidecarFlip (Mar 25, 2021)

I'd still have it repaired by a dealer in as much as you have never taken one apart. To replace the clutch you have to split the tractor. It's an involved job, especially for anyone who has never did it. Neither of mine have a dry clutch, just a damper plate.


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## Fedup (Feb 25, 2014)

I'm thinking your first assumption concerning the clutch slipping was probably pretty accurate. 

Farming out the repair is of course a decision you get to make if indeed that's the case. There are many many cases where individuals with no experience at it have done it "themselves" and been successful. It depends mostly on you. If you have the tools, reasonable mechanical skills, and most importantly a proper space to do it. You can learn a lot about your tractor and save some money to boot. 

There are multiple sources of information on "how to " do it, and plenty of help/answers/advice available if you're interested. No need to be afraid to try because some ex spurt tells you not to.


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## SidecarFlip (Mar 25, 2021)

I'm impressed you have the WSM. Most posters on here have no documentation, not even an owners manual so they basically haven't a clue about proper care and feeding....

If you have less than 1-1.5" off freeplay at the clutch pedal, it's out of adjustment but it don't really matter as you've already spun the clutch and once you spin a dry clutch (like you have), it glazed and shot and needs replacement and the flywheel will probably need turned and / or replaced if it's severely heat warped or discolored.

Again, I'd have an authorized Kubota dealer perform the work as it takes specialized tools to align the clutch and it entails splitting the unit plus they will use genuine Kubota replacement parts. Lots of clutch packages out there, mostly sub standard.

Why I purchased what I did, new and used. My units have no dry clutch which is the weakest point in any tractor driveline.

Having never owned a tractor or taken one apart (and splitting one is a major job, I believe you'd be in way over your head and the end result would most likely not be workable.

Sometimes it's better to bite the bullet and let someone with prior experience and knowledge do the work and pay for it, because, the end result will be a working unit.


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## SidecarFlip (Mar 25, 2021)

Fedup said:


> No need to be afraid to try because some ex spurt tells you not to.


Not sayin he cannot, what I'm saying is, for a positive result it's better to have a knowledgeable technician perform the repair. Anyone can do anything, given the time (and proper tools), but the end result may not be satisfactory and you know that.

Obvious to me the clutch is toast and the op stated it's his first tractor. In my opinion it would be better to have it done at a dealership.


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## gpsmatty (Dec 28, 2021)

SidecarFlip said:


> Not sayin he cannot, what I'm saying is, for a positive result it's better to have a knowledgeable technician perform the repair. Anyone can do anything, given the time (and proper tools), but the end result may not be satisfactory and you know that.
> 
> Obvious to me the clutch is toast and the op stated it's his first tractor. In my opinion it would be better to have it done at a dealership.


I totally understand where you're coming from on this, but I'm not the type of person to take something to the dealer unless it's under warranty, especially not a 30-year-old tractor. I bought this tractor not running which was reflected in the price and I went into it knowing it could need anything and even had an engine lined up to swap in if there were problems with the existing one. The only reason why it's my first tractor is I've never owned enough land to justify having one until now. I've done a 12v Cummins swap into a ford, replaced the CP4 pump on my LML Duramax when it blew, and have built at least 8 fox body mustangs not to mention multiple engine builds, and a lot of rebuilds after blowing stuff up at the drag strip. 

I've also been in the outdoor power equipment industry for 10+ years from the shop to the business side, and have worked on stump grinders, toro dingos, and have replaced engines, and drums in wood chippers.


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## gpsmatty (Dec 28, 2021)

Fedup said:


> I'm thinking your first assumption concerning the clutch slipping was probably pretty accurate.
> 
> Farming out the repair is of course a decision you get to make if indeed that's the case. There are many many cases where individuals with no experience at it have done it "themselves" and been successful. It depends mostly on you. If you have the tools, reasonable mechanical skills, and most importantly a proper space to do it. You can learn a lot about your tractor and save some money to boot.
> 
> There are multiple sources of information on "how to " do it, and plenty of help/answers/advice available if you're interested. No need to be afraid to try because some ex spurt tells you not to.


Yeah, it was my first thought, but after spending hours researching threads of similar tractors with similar issues I was hoping (wishful thinking) it could possibly be a hydraulic blockage or just something that needed to be adjusted. The big difference though was other people who were having shuttle issues were also having hydraulic issues with their FEL or 3 Point. Looking over the WSM and how the transmission worked led me to have someone check to see if the PTO turns off when it's "slipping", and when that was the case it seemed for sure it was the main single disk clutch slipping.

This is the tractor in question the day it came home


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## Fedup (Feb 25, 2014)

You're already better at troubleshooting than some of the "regular"s here and on other similar sites.


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## SidecarFlip (Mar 25, 2021)

Only Kubota's. I'm pretty well versed on them having owned at least 12 of them. The rest I don't know much about and don't need to.


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## SidecarFlip (Mar 25, 2021)

gpsmatty said:


> I totally understand where you're coming from on this, but I'm not the type of person to take something to the dealer unless it's under warranty, especially not a 30-year-old tractor. I bought this tractor not running which was reflected in the price and I went into it knowing it could need anything and even had an engine lined up to swap in if there were problems with the existing one. The only reason why it's my first tractor is I've never owned enough land to justify having one until now. I've done a 12v Cummins swap into a ford, replaced the CP4 pump on my LML Duramax when it blew, and have built at least 8 fox body mustangs not to mention multiple engine builds, and a lot of rebuilds after blowing stuff up at the drag strip.
> 
> I've also been in the outdoor power equipment industry for 10+ years from the shop to the business side, and have worked on stump grinders, toro dingos, and have replaced engines, and drums in wood chippers.


Have fun then and keep us apprised of your progress. It's a very involved job. First thing you need to do is remove the front end loader....


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## TX MX5200 (May 12, 2020)

Great if that’s within your wheel house….I don’t have the tools, knowledge or ability for a tractor split, but doesn’t mean you don’t. What really would scare me off is none of my friends do either so I would be stuck if I got it tore down.

I’ve swapped transmissions, motors, diffs and replaced clutches, throw out bearings and pressure plates before, but in jeeps, trucks and cars. I guess the tractor would be easier as the housing is all exposed…but the thought of it makes me skeeered. I will say, I ran an old Ford NAA (1953) for 19 years without clutch issues and imagine it was original. Guy at work had his neighbor split his full Utility John Deere this summer and wish I had known in advance so I could’ve handed wrenches and learned.


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## gpsmatty (Dec 28, 2021)

TX MX5200 said:


> Great if that’s within your wheel house….I don’t have the tools, knowledge or ability for a tractor split, but doesn’t mean you don’t. What really would scare me off is none of my friends do either so I would be stuck if I got it tore down.
> 
> I’ve swapped transmissions, motors, diffs and replaced clutches, throw out bearings and pressure plates before, but in jeeps, trucks and cars. I guess the tractor would be easier as the housing is all exposed…but the thought of it makes me skeeered. I will say, I ran an old Ford NAA (1953) for 19 years without clutch issues and imagine it was original. Guy at work had his neighbor split his full Utility John Deere this summer and wish I had known in advance so I could’ve handed wrenches and learned.


After having done the clutch on this tractor, I would say based on other things you've done you can easily handle it. I found it a bit easier than to do a clutch in say a 4WD with a heavy transmission on T case attached.


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## gpsmatty (Dec 28, 2021)

Here's a long update, the single disk clutch was smoked, and replacing it went smooth. The tractor is actually useable now, but it is still slipping and this time I can confirm it's coming from the clutch packs inside the trans.


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## gpsmatty (Dec 28, 2021)

Now for part two, the tractor is a lot more useable now and I've been able to get some stuff done around the property, but it is still slipping in high gear under load.










Went back in and pulled apart the flow priority valve, didn't look like there was any obstructions and the plunger moved freely.


























Next, I checked the plungers on the shuttle shift valve because the WSM talks about shims to increase pressure, well someone was already in there and put over double the number of shims than came factory on one of the plungers, and a couple of lock washers for good measures as shims on the other. I'm going to put the shims back to factory spec and test oil pressure coming off the circuits on the shuttle shift valve. If oil pressure is low then I need to figure that out, otherwise if pressure is good, I'll split the trans and this time replace the clutches and plates in the shuttle shift clutch packs.


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## SidecarFlip (Mar 25, 2021)

High gear should NEVER be used in any HIGH LOAD scenario


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## gpsmatty (Dec 28, 2021)

SidecarFlip said:


> High gear should NEVER be used in any HIGH LOAD scenario


Obviously.


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## gpsmatty (Dec 28, 2021)

I said In high as a generalization. It will slip in low in 3rd going up a steep enough hill and will slip in high as soon as you hit any incline. It will even slip in 1st low in some situations. Other hydraulic shuttle tractors I've operated would kill the engine before the shuttle started slipping.


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## SidecarFlip (Mar 25, 2021)

If that is the case, you have one of 2 scenario's going on. Either the clamping pressure is too low (which can be adjusted at the proportioning valve (mine has a hex bolt and lock nut for that) or the pack plates are shot and need replaced. Like I said earlier the only way to access the clutch pack is a split. You can see it from the back (if you remove the pto carrier plate in the back, but you cannot access it. because it's in front of the final drive components. I suspect it's been slipped enough that the plates are glazed or shot. I also presume you have a Kubota Workshop manual for it? If you don't, go to www.kubotabooks.com and download a copy, it should be listed there. The constantly rotating PTO stub tells me the brake plates at least are shot. Constant stub rotation is a classic sign of that issue.

Kubota's have notoriously weak pto clutch brakes. They only use one pair of driven plates and one steel and why on both my M's, I run an over running coupler on any implement that will freewheel when the pto is disengaged. Some of my implements have built in over running clutches, some don't. A classic implement that don't is a brush chopper or rear mount finish mower.

I've never had to adjust the clamping pressure or the pack pressure but I bought them both new way back in 2002 and 2004 and I knew going in that the pto brakes especially were weak so I'm always careful and I always have an over running clutch on the pto stub where required. Kubota issued an RO for mine but I never followed through on it because I knew going in about the issue and took necessary steps to mitigate it. One of mine has in the excess of 6000 meter hours on it and the other has 2000+.

The one thing you never want to have happen is, the implement drives the pto stub when the pack isn't pressurized, ever.

With the pto off and the engine off, grabbing the stub and turning it manually, the stub should only rotate 180 degrees in either direction. Kubota builds that rotation in so you can hook up a pto shaft easily. Past 180, it should come up against the brake and you should be able to hear it as well.

If the pto pack is shot, I suspect the travelling pack is as well.


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## SidecarFlip (Mar 25, 2021)

Both mine will kill the motor at idle or spin the wheels if running at rpm. Myself, I prefer the wet travelling pack and pto pack over any other method because parasitic losses are very minimal and in reality aren't complex, unlike a CVT or a hydrostat.


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## SidecarFlip (Mar 25, 2021)

Pretty obvious to me the original owner flogged the hell out of it before he got sick.


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## gpsmatty (Dec 28, 2021)

SidecarFlip said:


> Pretty obvious to me the original owner flogged the hell out of it before he got sick.


That's for sure!


I have an update

I posted this on a couple of forums and forgot to update my progress here. I got my pressure tester and was getting about 42 PSI out of each circuit (on the hydraulic shuttle valve) Forward/Lubrication/Reverse. I pulled the valve out took it as far apart as I could using compressed air to blow out circuits of any crud reassembled and unfortunately the same thing. The next step was to remove the outlet line and test pressure off that VS off the pressure testing ports to see if there was a pleasure leak inside of the transmission. Same thing. I then tested the pressure out of the flow priority valve and it was more than my gauge and hose could handle, but it told me the pressure was good out of the priority valve. 

My last step:
Ordered a used Shuttle control valve off ebay from an L3750 swapped it in and the problem was solved. I plan to pull the old control valve apart again for a second look to try and pinpoint the exact problem, but the relief valve for the lubrication circuit was bleeding off pressure for all control valve positions.


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## SidecarFlip (Mar 25, 2021)

Read your comment on the other forum. Happy for you.


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