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.