Differential lock broken pins?

[Rosohatica]

You will need to do a tear down if it's damaged, the top cover will only let you see it.

How complicated is this repair if it proves that dogs are broken? I will get a quote from the Kubota repair shop tomorrow, but I am scared of the bill, so I am already thinking of trying to fix it myself. Can it be done? So far my best mechanic achievement was repairing a bicycle 🥲. Otherwise I am handy with tools but totally different field, woodworking.

 

[North Idaho Wolfman]

How complicated is this repair if it proves that dogs are broken? I will get a quote from the Kubota repair shop tomorrow, but I am scared of the bill, so I am already thinking of trying to fix it myself. Can it be done? So far my best mechanic achievement was repairing a bicycle 🥲. Otherwise I am handy with tools but totally different field, woodworking.

I personally think it's a rather simple repair.
But I'm probably not the best to ask as nothing on that tractor seems complicated to repair.

I would open up the top and that would let you see what your dealing with.
It might be as simple as a sheared pin.

 

[Russell King]

Thanks for the hint. Indeed, I missed that detail. I will take a look as soon as I get to the tractor. Meanwhile I tried to search for the dimensions of the pin. Attached find an image. It looks like it is rather long. I guess it is around 1.375 inches and I assume shaft rod is around 0.5 inches which means pin would be sticking out on each side.
View attachment 167334

You might just take this linkage apart and see if the rod into the tractor can be rotated by hand with some locking pliers.

Taking the top off only lets you see it, not fix it (if the pins are sheared) as NIW stated. I think you may be able to pry it back if it is stuck in position and the pins are not sheared. It is just a lot less work than getting there from the sides (as I see it).

 

[Rosohatica]

You will need to do a tear down if it's damaged, the top cover will only let you see it.

Depending on the damage you might need to get into both sides, but you would start by getting to it on the left side housing.

View attachment 167342

View attachment 167343

Left even the foot lever is on the right side? And do I need to remove the top just for the diagnosis or for repair as well? Any special tools required? Thanks in advance.

 

[Rosohatica]

You might just take this linkage apart and see if the rod into the tractor can be rotated by hand with some locking pliers.

Taking the top off only lets you see it, not fix it (if the pins are sheared) as NIW stated. I think you may be able to pry it back if it is stuck in position and the pins are not sheared. It is just a lot less work than getting there from the sides (as I see it).

I think it is not only stuck because foot lever would be stuck as well at down position. Since everything is sealed I am thinking of a way of making minimal damage to the seals. So if opening sides is needed for the repair work anyway - is opening of the top required for repairment also ( I understand that alone is not enough, except in the case you described here)? Or it is just the easiest way to get to diagnosis?

 

[Russell King]

As I understand it the repair can be made with the top left on. Assuming that the pins are sheared or stuck. Other repairs like a sheared pin in the linkage will require the top to be removed if the sheared pin is internal.

The left side (sitting on tractor) is where the different pin carrier is installed.

But if you need to get the actual differential out of the tractor then both sides and the top have to be removed.

That is the way I see the assembly anyway. I have never taken one apart in my life though.

As far as difficulty level, it is all in the upper half of easy to difficult. I would guess at 6-7 out of 10. The parts may be pretty heavy and gears can certainly pinch fingers hard. But if you use a wood lathe you are likely aware of that type of danger, I am pretty sure you could do it in an enclosed shed with a solid floor. I would NOT recommend doing it in a muddy field unless you built a wooden (heavy duty) floor and some tarp (tent) over the tractor to keep rain and snow out.

I still recommend getting the top off first to see what is going on - since the locking pins seem to be substantial AND you have not said anything about a loud popping sound when you applied the differential lock.

 

[North Idaho Wolfman]

You need to pull the top cover first as your repair could be as simple as replacing pin 020 and keeper 030. (yellow).
Pin number 020 goes through shaft 040 and if that pin is broken or missing then the diff lock fork will not move to disengage the locking collar (green part).
The likelihood that you have broken the engagement pins on the locking collar is really rare!

 

[Russell King]

@North Idaho Wolfman
How does the differential lock pin plate get moved into and away from the holes? I just see the pedal rotating shaft #40 which moves the fork in rotation? I think I may see a slot at the top of part #10 that may allow pin #20 to move the fork back and forth- if that slot is a helix shaped slot.

Sorry for being so curious but I can’t locate a picture of the fork to see how the slot looks.

 

[North Idaho Wolfman]

@North Idaho Wolfman
How does the differential lock pin plate get moved into and away from the holes? I just see the pedal rotating shaft #40 which moves the fork in rotation? I think I may see a slot at the top of part #10 that may allow pin #20 to move the fork back and forth- if that slot is a helix shaped slot.

Sorry for being so curious but I can’t locate a picture of the fork to see how the slot looks.

Yes the fork has a helical slot that when the shaft and pin is rotated pushes the lock in and out of the differential.

 

[Rosohatica]

As I understand it the repair can be made with the top left on. Assuming that the pins are sheared or stuck. Other repairs like a sheared pin in the linkage will require the top to be removed if the sheared pin is internal.

The left side (sitting on tractor) is where the different pin carrier is installed.

But if you need to get the actual differential out of the tractor then both sides and the top have to be removed.

That is the way I see the assembly anyway. I have never taken one apart in my life though.

As far as difficulty level, it is all in the upper half of easy to difficult. I would guess at 6-7 out of 10. The parts may be pretty heavy and gears can certainly pinch fingers hard. But if you use a wood lathe you are likely aware of that type of danger, I am pretty sure you could do it in an enclosed shed with a solid floor. I would NOT recommend doing it in a muddy field unless you built a wooden (heavy duty) floor and some tarp (tent) over the tractor to keep rain and snow out.

I still recommend getting the top off first to see what is going on - since the locking pins seem to be substantial AND you have not said anything about a loud popping sound when you applied the differential lock.

Thanks, no I have not heard any popping sound. I have a wooden garage where I could do it. It has dry wooden floor above from the ground and solid roof. However now it is wintertime so there is a LOT of condensate on the tractor. During the night metal gets cold and during the day it warms up a bit so all over the surface outside metal parts are completely wet from the condensate. I am afraid if I am to open the tractor, water will come into inside as well. Somehow I think that is a very bad thing.

 

[Rosohatica]

You need to pull the top cover first as your repair could be as simple as replacing pin 020 and keeper 030. (yellow).
Pin number 020 goes through shaft 040 and if that pin is broken or missing then the diff lock fork will not move to disengage the locking collar (green part).
The likelihood that you have broken the engagement pins on the locking collar is really rare!


View attachment 167353

Thanks. Understood. I wish only this would be the case. I guess I will know once opened. I called Kubota repair shop. They said this is a common case and that usually just one of the 8 engagement pins breaks, but it gets stuck and it keeps the differential locked, while remaining 7 pins can easily go in and out since the locked one is holding the position where remaining pins match the holes - position is kept by the locked pin and therefore the pedal goes easy down and up=pins going in and out.

 

[D2Cat]

Thanks. Understood. I wish only this would be the case. I guess I will know once opened. I called Kubota repair shop. They said this is a common case and that usually just one of the 8 engagement pins breaks, but it gets stuck and it keeps the differential locked, while remaining 7 pins can easily go in and out since the locked one is holding the position where remaining pins match the holes - position is kept by the locked pin and therefore the pedal goes easy down and up=pins going in and out.

Interesting. Good to know. Thanks.

 

[Rosohatica]

Hi all, here is the update. Tractor has been opened at the repair shop.
After opening the rear axle, the issue was found in the differential lock dog clutch.
One or two “fingers” (dogs) are partially chipped, and two of them show darker discoloration compared to the others - look at the image attached. On the image you can see two of them darker in color and one can be seen lighter in color (healthy color).
The repairman said discoloration appears consistent with overheating caused by partial engagement and slipping under load. At this point, the plan is to replace the diff lock dog clutch, followed by a full cleaning and oil change.

 

[ruger1980]

Hi all, here is the update. Tractor has been opened at the repair shop.
After opening the rear axle, the issue was found in the differential lock dog clutch.
One or two “fingers” (dogs) are partially chipped, and two of them show darker discoloration compared to the others - look at the image attached. On the image you can see two of them darker in color and one can be seen lighter in color (healthy color).
The repairman said discoloration appears consistent with overheating caused by partial engagement and slipping under load. At this point, the plan is to replace the diff lock dog clutch, followed by a full cleaning and oil change.

I would honestly not change the due to color, but only of the pins are bent or damaged beyond repair. . If the dog clutch engages smoothly I would leave it be. if it does not engage smoothly I would clean up the pins so that it does and put it back together.

Going forward only engage the diff lock while the wheels are not spinning

 

[Rosohatica]

I would honestly not change the due to color, but only of the pins are bent or damaged beyond repair. . If the dog clutch engages smoothly I would leave it be. if it does not engage smoothly I would clean up the pins so that it does and put it back together.

Going forward only engage the diff lock while the wheels are not spinning

That was my initial thought as well. The mechanic’s view is that it likely got stuck due to some chipping and partial engagement, but he can’t be 100% sure until it’s opened further. For now, only the top cover has been removed.

Visually, none of the dogs appear fully broken. The question I have is whether what you’re suggesting (cleaning/dressing the dogs so they engage smoothly) can realistically be done without splitting the tractor further. If there’s no practical way to do that without opening it up anyway, then I’d honestly feel more comfortable replacing the dog clutch while I’m in there — it’s not a particularly expensive part compared to the labor involved.

That said, if there is a way to clean up the dogs, check for loose or cracked fragments, and confirm everything is sound without fully tearing the rear end apart, I’d definitely like to know.

And yes — lesson learned. Diff lock will only be engaged with no wheel spin going forward

 

[ruger1980]

That was my initial thought as well. The mechanic’s view is that it likely got stuck due to some chipping and partial engagement, but he can’t be 100% sure until it’s opened further. For now, only the top cover has been removed.

Visually, none of the dogs appear fully broken. The question I have is whether what you’re suggesting (cleaning/dressing the dogs so they engage smoothly) can realistically be done without splitting the tractor further. If there’s no practical way to do that without opening it up anyway, then I’d honestly feel more comfortable replacing the dog clutch while I’m in there — it’s not a particularly expensive part compared to the labor involved.

That said, if there is a way to clean up the dogs, check for loose or cracked fragments, and confirm everything is sound without fully tearing the rear end apart, I’d definitely like to know.

And yes — lesson learned. Diff lock will only be engaged with no wheel spin going forward

Do the pins of the dog clutch slide in and put of their respective holes without binding? IF so you probably don't need to dress the pins but you could clean them up with a strip of emery paper. You should be able to slip that around each individua pin and clean them up.

I am pretty certain that any slipping of the dog clutch did not cause enough heat to blue the pins.

 

[TheOldHokie]

That was my initial thought as well. The mechanic’s view is that it likely got stuck due to some chipping and partial engagement, but he can’t be 100% sure until it’s opened further. For now, only the top cover has been removed.


Visually, none of the dogs appear fully broken. The question I have is whether what you’re suggesting (cleaning/dressing the dogs so they engage smoothly) can realistically be done without splitting the tractor further. If there’s no practical way to do that without opening it up anyway, then I’d honestly feel more comfortable replacing the dog clutch while I’m in there — it’s not a particularly expensive part compared to the labor involved.


That said, if there is a way to clean up the dogs, check for loose or cracked fragments, and confirm everything is sound without fully tearing the rear end apart, I’d definitely like to know.


And yes — lesson learned. Diff lock will only be engaged with no wheel spin going forward

Well I can't see much in that picture. Just guessing but I would think the clutch can be accessed without a "split" by removing the axle housing on that side. I"ve separated the axle on a B7200 multiple times and it was a simple job. This is where a WSM pays for itself.

Dan

 

[Rosohatica]

Do the pins of the dog clutch slide in and put of their respective holes without binding? IF so you probably don't need to dress the pins but you could clean them up with a strip of emery paper. You should be able to slip that around each individua pin and clean them up.

I am pretty certain that any slipping of the dog clutch did not cause enough heat to blue the pins.

Thanks for your thoughts. My understanding by what the mechanic’s told me is that partial engagement under load can create very high localized contact temperatures, even if bulk heating is limited, and that once material has chipped, the remaining edges become more prone to catching or further damage under torque — even if everything slides freely when unloaded.
I will double check with the mechanic tomorrow to see what he says further. Honestly I am not sure if operation is smooth at the moment.

 

[Rosohatica]

Well I can't see much in that picture. Just guessing but I would think the clutch can be accessed without a "split" by removing the axle housing on that side. I"ve separated the axle on a B7200 multiple times and it was a simple job. This is where a WSM pays for itself.

Dan

Thanks Dan. I guess you are saying it would be enough to open just one side of the tractor?

 

[North Idaho Wolfman]

Thanks Dan. I guess you are saying it would be enough to open just one side of the tractor?

I think you'll be able to pull the parts you need to pull just opening up the left side.