4WD/locking diff, slippage possible/'normal'?

[Coyote machine]

Using my 40HP Diesel Kioti DK-40 with HST transmission and 6' bush hog. Pushing uphill backwards in 4wd is it possible to get slippage at one rear wheel without it being a problem? Also, with same scenario, but with diff locked by diff lock pedal the same thing happens at a certain point, the tractor just will not go any further and the left rear wheel starts to spin. NOTE: The grass is NOT dry so it may be loosing traction because of that and tearing it up until it reaches dirt/mud.
Just haven't encountered this type of thing before. Usually I have the backhoe on and it provides 1000+#s of ballast and I'm not running the PTO at PTO 540 speed. Then if I'm already spinning in snow or mud I put it in low and lock the diff and it will get me unstuck.
Is it possible the HST reaches it's limit and just has no more power to give and the wheel starts to spin because of reaching the limit on trying to push/pull the tractor uphill?
It also might be possible the grade is causing the frame to bottom out, but I don't see it as being steep enough to do so.

TIA for any thoughts/answers.....

CM

 

[100 td]

If a wheel spins then it is has lost traction, drive is transferred to the easiest path. By locking the diff, you would have to spin both wheels together if it is a proper diff lock. (A lot of diff locks only lock while you have your foot continuously on the pedal). When you go up a hill in reverse it's like driving a front wheel drive car up a slope forwards, the load is transferred to the downhill section (rear) of the car, not on the uphill, front drive axle, and the front wheels are easily spun. Your rear wheels are now the same as the front wheel drive car.

 

[k0ua]

Is it possible the HST reaches it's limit and just has no more power to give and the wheel starts to spin because of reaching the limit on trying to push/pull the tractor uphill? No, the HST still is delivering power to the drivetrain, but you have just lost traction. There are plenty places around my house where that occurs.
It also might be possible the grade is causing the frame to bottom out, but I don't see it as being steep enough to do so. Probably not dragging the frame, you just have found a steep spot where you are not getting enough traction to keep moving.

If the differential lock is working correctly when it engages, and you feel the pedal go down, it should be spinning both wheels. Instead of using the differential lock, you can also unlock your split brakes when one wheel starts to spin, apply a bit of brake to that wheel and your differential action will apply more power to the wheel that is not spinning. Do this is short bursts to get moving again. I usually use this method instead of the differential lock to keep moving.

 

[k0ua]

If you are in HI range it is possible for the HST relief valve to open and not spin any wheels and not move. If for instance you push up against an immovable object and ground traction is very good. If you shift to a lower range, then a wheel/wheels will spin.

 

[LD1]

If diff lock is engaged and properly functioning, both rears should be locked together and spin at the exact same speed.

Are you saying this ain't happening? If not, something ain't right with your diff lock or engagement proceedure

 

[Coyote machine]

It's possible I may not have had the diff locked and just been in 4wd in low range, and one rear wheel spinning. The Kioti tech at the dealer said if in 4wd only, (no diff lock engaged) it should be one front and one rear spinning simultaneously.

LD1 is it possible for one rear wheel to spin if on wet grass or similar, with the diff locked?
Does the PTO running the bush hog have any bearing on what the HST can output to the wheels/drivetrain?
Would there be any difference if the PTO were NOT engaged?

James, why wouldn't you use the diff lock instead of splitting the brakes? It's easy to hold the pedal down, vs. disconnecting the brake split bar, no?

 

[LD1]

If diff lock is engaged and working properly, it is not possible for only one wheel on the back to spin and the other not.

I keep my brakes unlocked. It's almost natural to hit one if spinning. And can be done on the fly if one wheel starts to slip. Diff locks usually cannot be applied if one wheel is spinning and one isn't. They have to be going the same speed or stopped. So you either have to be proactive and apply before needed, or come to a stop then apply and try again.

 

[Coyote machine]

LD1,
You're right, of course, and it reminds me that I probably did not have the diff locked, but was in 4wd and had one rear spinning. It was a difficult position to be in, backing up hill trying not to scalp the area with the bush hog, trying to back up the slope at an angle as far as the tractor would allow. So I was twisted to the right, looking over my right shoulder, trying to engage the reverse pedal and that would not have allowed me to engage the diff lock with the heel of my left foot, because I was so twisted to the right I would not have likely been able to get my foot on the pedal to engage it before it was already spinning. Then if I tried to lock it, as you said, it would not have been possible.
I'll maybe try it again tomorrow and see what exactly is/was happening when I was getting slippage.
So just to clarify, slippage can occur in 4wd, (obviously), but not with diff locked. That is why one would go to locked to begin with, to prevent slippage, before it might occur, or after it begins, by stopping movement, then engaging the lock, correct?

 

[LD1]

Correct. Sounds like your diff lock might be a pain to engage. I know mine is. Stiff, small pedal with the heal of the right foot. I just find it easier and more natural to use split braking. And just as efficient

 

[k0ua]

If diff lock is engaged and working properly, it is not possible for only one wheel on the back to spin and the other not.

I keep my brakes unlocked. It's almost natural to hit one if spinning. And can be done on the fly if one wheel starts to slip. Diff locks usually cannot be applied if one wheel is spinning and one isn't. They have to be going the same speed or stopped. So you either have to be proactive and apply before needed, or come to a stop then apply and try again.

What he said^^ I use split braking more than diffy lock. I also use split braking a lot when plowing snow to keep a straight line and sometimes when working dirt up next to a building for adjustments to hold your travel line when your work is skewing the tractor sideways slightly, it is often more effective to counter these forces with the split brakes. I think a lot of people put a lot of strain on their differential lock by engaging it while a wheel is spinning but split brake application is in my opinion faster, more natural at at least as effective if not more so.

 

[k0ua]

When you have to stop to engage the differential lock, you sometimes lose what momentum you have and you often find yourself with now two rear wheels spinning and you are still stuck. If have found it is often better to when you notice one rear wheel spinning to use the split brakes and you are often moving again in a fraction of a second.

 

[LD1]

When you have to stop to engage the differential lock, you sometimes lose what momentum you have and you often find yourself with now two rear wheels spinning and you are still stuck. If have found it is often better to when you notice one rear wheel spinning to use the split brakes and you are often moving again in a fraction of a second.

That has been my experience as well. Usually the only time my brakes get locked is when setting the brake to chain to the trailer.

And you are spot on about using them when grading or plowing snow with an angled blade.

 

[Everhard]

And one other thought regarding the diff lock - once applied it'll make the tractor harder to turn (depending on the ground) as it'll want to drive straight, (annoying if you're in a position where you're trying to turn) and often as long as power is maintained to the rear wheels it won't unlock immediately which can be a pain if you transition out of a poor traction area to somewhere where you have plenty of traction - especially if you try to turn at that point.

Personally I generally only use the diff-lock for times when neither wheel is getting good traction. At that point having a differential is of little use. any other time I'd rather use the brakes as mentioned by other posters.

E.

 

[Coyote machine]

I figured out the problem: It was operator error. Either I didn't get my left foot on the diff lock pedal, or I didn't get it pressed down far enough to get it to engage. Either way that's why one rear was spinning.
Thanks for all the input guys.

Now I have another question. I seem to remember my selling dealer telling me to keep the brake pedals locked. What are the downsides of unlocking them? I've always used them as a locked unit. I seem to recall reading or someone telling me that with them unlocked it's possible to roll the tractor, accidentally? Or something equally un-fun?

I can see the advantages of what you guys are saying about plowing snow, and other things like not loosing momentum already built up and how fast the brakes being split could get one back on the task at hand without having to come to a full stop, and then trying to gain lost momentum, etc.

 

[Everhard]

If you're travelling fast then yes, for safety having both brakes linked is a good idea, particularly if you're in a hilly area. The other time I lock mine is if I'm setting the parking brake and it's a decent slope - that way both are engaged.

As for rolling the tractor - if you're travelling at high speed, and engage one brake hard I suppose it's possible to cause the tractor to suddenly spin on that one wheel which in turn can cause the tractor to roll particularly on a downhill.

As for leaving them engaged - That would depend on what you are doing in my mind. General low speed work (field work, around the barn, on the trails etc) I'd always have them separated so that I can use them independently. Your usage might differ and you might spend a lot of time travelling in which case it might be a good idea to keep them combined. Or lastly be mindful of getting your foot on both pedals and engage both at the same time. (Personally I guess after so many years of using the separate brakes it becomes instinct to select left/right/both as the situation dictates.)

Btw - on a side note, just because both brakes are linked together doesn't mean they will both apply the same stopping force on each wheel - that entirely depends on how well the tractor brakes are maintained - which is why it's a good idea to check them periodically.

E.

 

[Coyote machine]

If you're travelling fast then yes, for safety having both brakes linked is a good idea, particularly if you're in a hilly area. The other time I lock mine is if I'm setting the parking brake and it's a decent slope - that way both are engaged.

As for rolling the tractor - if you're travelling at high speed, and engage one brake hard I suppose it's possible to cause the tractor to suddenly spin on that one wheel which in turn can cause the tractor to roll particularly on a downhill.

As for leaving them engaged - That would depend on what you are doing in my mind. General low speed work (field work, around the barn, on the trails etc) I'd always have them separated so that I can use them independently. Your usage might differ and you might spend a lot of time travelling in which case it might be a good idea to keep them combined. Or lastly be mindful of getting your foot on both pedals and engage both at the same time. (Personally I guess after so many years of using the separate brakes it becomes instinct to select left/right/both as the situation dictates.)

Btw - on a side note, just because both brakes are linked together doesn't mean they will both apply the same stopping force on each wheel - that entirely depends on how well the tractor brakes are maintained - which is why it's a good idea to check them periodically.

E.

Thanks, E. That sounds like a good plan. I will try them unlocked in different situations and see how it feels. It will be different because I have 1100-1200 hours of locked brakes as my experience in using tractors to date. So I have no other reference, but I can see what the possible benefits are, especially if I put my foot on both at the same time for 'normal' braking. And locking them together if leaving the tractor, in addition to the parking brake is a good idea too. Now I can try some donuts, and maybe some wheelies or sliding parallel parking tricks, huh! :laughing:

 

[Everhard]

Lol, have fun with it! Take some video's if you manage a sliding parallel park...

On a more serious note - while you're playing with it, one of the big benefits "tricks" is to help the tractor turn. If you ever find yourself in a situation where you turn the wheel and the tractor keeps going straight or doesn't turn as much as you'd expect it to for the given turn of the wheel then you can help it turn by pressing the inside wheel brake. (In fact you can do a donut lol!) That's what I use them for the most come to think about it. I'm guessing you don't do field work? But you do logging etc - on trails do you ever find you have to fight the tractor to make it turn? That would be the perfect time to use them.

Like you said play with them, they are another tool in the tool box.

E.

 

[k0ua]

Coyote you will discover that your tractor is ideal for split brake usage as the brakes are on the left and the "go pedals" are on the right. And since most of us only come equipped with two legs/feet, that works out pretty well. As stated, there are times to have them locked together and there are times to have them split, ready for rapid application of just one brake for various reasons.

I am surprised you haven't tried it when pushing snow/ice. Many times you have no directional control by using the steering wheel/front wheels, and the only way to maintain directional stability is by using your split brakes.

You will notice when you split the brakes, there will be a red warning lamp on the dash lit up warning you of that fact. They don't want you to go flying down the road and just hitting one brake. Of course that could throw you into the ditch. But there are many times split brakes can be useful, you just need to practice and know when/how to use them.

 

[Coyote machine]

Lol, have fun with it! Take some video's if you manage a sliding parallel park...

On a more serious note - while you're playing with it, one of the big benefits "tricks" is to help the tractor turn. If you ever find yourself in a situation where you turn the wheel and the tractor keeps going straight or doesn't turn as much as you'd expect it to for the given turn of the wheel then you can help it turn by pressing the inside wheel brake. (In fact you can do a donut lol!) That's what I use them for the most come to think about it. I'm guessing you don't do field work? But you do logging etc - on trails do you ever find you have to fight the tractor to make it turn? That would be the perfect time to use them.

Like you said play with them, they are another tool in the tool box.

E.

Th only real field work is when I'm bush hogging land I need to bring back to pasture, so a lot this Fall. I just knock stuff down with the tractor if it's needs to turn in tight spaces!
I've got a tree shear coming next week so I may be making some new paths through the wood lands, hopefully! This thing will cut a 12" diameter tree and drop it in one bite!!:cool2:

Coyote you will discover that your tractor is ideal for split brake usage as the brakes are on the left and the "go pedals" are on the right. And since most of us only come equipped with two legs/feet, that works out pretty well. As stated, there are times to have them locked together and there are times to have them split, ready for rapid application of just one brake for various reasons.

I am surprised you haven't tried it when pushing snow/ice. Many times you have no directional control by using the steering wheel/front wheels, and the only way to maintain directional stability is by using your split brakes.

You will notice when you split the brakes, there will be a red warning lamp on the dash lit up warning you of that fact. They don't want you to go flying down the road and just hitting one brake. Of course that could throw you into the ditch. But there are many times split brakes can be useful, you just need to practice and know when/how to use them.

When to fold and when to hold. What me flying down the road?! Say it ain't so....
I will have to try it on the driveways this winter. I use a suicide knob on my steering wheel, and with split brakes I see the sliding parallel parking job being easy as cake.

 

[prs]

Coyote, seems like you have it figured out. I do recall a time when with my differential lock engaged only one rear wheal was spinning. But, the diagnosis was a broken spur gear Doubt you have that. I 4WD and diff locked, you still have an open front axle. One neat trick if using AG or IND tires, run the fronts with tread backward. That way they push you up hill very well, provide super braking when coming down steep slippery slopes and with a heavy loader they push up instead of digging in too deep.

prs