Diff Scare

[bluedunn]

Well that was scary - I got my BX stuck on some slippery ground in the woods yesterday. In an effort to get myself unstuck, I thought I misapplied the diff. lock which I thought resulted in me breaking the pins. After thinking I did this (and mentally panicking), I didn't notice any unusual behavior from the HST so I just kept working and didn't try the diff again (mostly hoping I hadn't just busted my transmission).

This fact nagged at me all night, so I just went out, bit the bullet, and gave it a try. Seems to engage just fine, after a bit of fiddling. I say fiddling because it's not the easiest feature to engage, but it does engage.

So this leads me to a question...how would one know that the diff lock was broken? Would it make a horrible sound if the pins shear off? Would the HST fail altogether? Would the diff lock pedal not completely engage?

Thanks!

 

[Roadworthy]

How one would know the differential lock was broken would probably be determined by the manner of breakage. The lock itself is unlikely to be part of your transmission. Its job is to engage or lock both rear wheels together for a true two wheel drive at the rear of the tractor. It should never be engaged while the wheels are moving. If it breaks, unless something jams, your tractor should operate normally. I don't know this for sure - I've never broken one.

 

[nbryan]

The diff lock on my B2650 won't engage usually until the rear tires start to rotate at different speeds, like when one tire spins free on a slippery surface and the other holds at a stop - ie. the differential is slipping like it should. With good traction on both wheels they both turn together and the diff lock engagement pin won't necessarily be in alignment inside the diff to engage to lock the drive shafts. You have to get one wheel spinning relative to the other while pressing down on the lock lever.

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[bluedunn]

Interesting...

So when I was testing mine yesterday, I was able to push down on the diff lock pedal and it did engage, but it wasn't instantaneous - like the pins had to line up with the engagement holes (probably not the technical term). At this point I about 99% certain I didn't break anything since I was able to get the pedal to go all the way down after some very slow rolling of the tractor.

 

[twomany]

A look at the exploded parts illustration for your tractor will be the best resource for your concerns.

Diff locks are a SINGLE pin, that must slide into a hole.

When you step on the diff lock pedal, you apply PRESSURE to the mechanism. It is not until the pin and holes line up that MOTION / ACTUATION occurs.

There is a spring to release the engagement. "when the time is right">

My Hurlimann tractor has a hydraulic diff lock engagement system. ON THE FRONT AXLE!>

 

[North Idaho Wolfman]

99% of the time when you break the diff lock pins on that model, you'll know it super quick, because they will pop right out the bottom of the case, there's no room under the diff for spare/ broken parts.

 

[nbryan]

Interesting...



So when I was testing mine yesterday, I was able to push down on the diff lock pedal and it did engage, but it wasn't instantaneous - like the pins had to line up with the engagement holes (probably not the technical term). At this point I about 99% certain I didn't break anything since I was able to get the pedal to go all the way down after some very slow rolling of the tractor.

Yes that's my experience. I'm finding it super useful to use the lock in some slick snowy conditions even with 4WD going. And using the brake pedal split can also be an effective steering aid.

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[Zaicran]

I might be an oddball..but I grew up around tractors and have been driving them/working them since I was 12.

I don't really use the rear diff lock much if at all...my method is to apply brake to the wheel that wants to spin...which sends more power over to the other wheel equal to the amount I am braking the spinning wheel. Mostly because I am too lazy to stop, hit the diff lock, and then go again..I just pay attention and if a wheel is spinning, I brake it slightly.

This works for me, but your situation might have been different.

 

[bluedunn]

I might be an oddball..but I grew up around tractors and have been driving them/working them since I was 12.

I don't really use the rear diff lock much if at all...my method is to apply brake to the wheel that wants to spin...which sends more power over to the other wheel equal to the amount I am braking the spinning wheel. Mostly because I am too lazy to stop, hit the diff lock, and then go again..I just pay attention and if a wheel is spinning, I brake it slightly.

This works for me, but your situation might have been different.

That would be nice, but my BX doesn't have split brakes...obviously the answer is to get a bigger tractor with this feature ;-)

 

[Zaicran]

That would be nice, but my BX doesn't have split brakes...obviously the answer is to get a bigger tractor with this feature ;-)

Yup like I said, you're situation might be different.

 

[Stmar]

That would be nice, but my BX doesn't have split brakes...obviously the answer is to get a bigger tractor with this feature ;-)

My 8Ns only had one brake pedal and I would just put a bit of pressure on the single pedal and it acted like a diff lock. With 8Ns everything was old school, they were as old as me so not much technology built in.

 

[Henro]

My 8Ns only had one brake pedal and I would just put a bit of pressure on the single pedal and it acted like a diff lock. With 8Ns everything was old school, they were as old as me so not much technology built in.

Great idea I will have to try on my BX.

But since the treadle directional pedal is on the same side as the brake, it would be better if I had two right legs... But I am sure it can be done.

One thing that absolutely does not register with me, is the idea that the diff lock must be applied when the wheels are not moving. Cannot see how one could have much of a chance of getting a pin in a hole that way, even if there were multiple holes for the pin to fall into. Seems like the odds would be against it happening. Is one supposed to keep moving/stopping the wheels multiple times, and at each stop trying the diff lock, until it happens to find the hole?

Can someone set me straight on this?

 

[twomany]

Great idea I will have to try on my BX.

But since the treadle directional pedal is on the same side as the brake, it would be better if I had two right legs... But I am sure it can be done.

One thing that absolutely does not register with me, is the idea that the diff lock must be applied when the wheels are not moving. Cannot see how one could have much of a chance of getting a pin in a hole that way, even if there were multiple holes for the pin to fall into. Seems like the odds would be against it happening. Is one supposed to keep moving/stopping the wheels multiple times, and at each stop trying the diff lock, until it happens to find the hole?

Can someone set me straight on this?

Perhaps a better instruction would be to not engage the diff lock while the one wheel is spinning. The method is to tread on the pedal sufficiently to pressure the pin towards engagement, THEN actuate the go pedal/ let out the clutch to have the wheels turning. Both wheels turning, but at slightly different rates is the ideal!

The idea is that with continuous pressure on the engagement pin, it will find it's way home as soon as the hole comes around. A rapidly spinning diff member very well may send the hole past the pin too quickly for the pin to drop in. That would snub across the pin end, wearing, deforming or even shearing the pin, while rounding over the hole edge.

The engagement of the diff lock (split diff down under) is not a "position" as we think of a range selector, or a stick shift on a transmission. It is a spring return pin, that needs to be pushed into a hole. once in the hole, the friction between hole and pin, along with continued pedal pressure maintains engagement.

Don't step hard on the pedal, don't step on the pedal while stuck and spinning. DO anticipate the need for a locked diff and lock it up while approaching the trouble spot.

Let off the pedal and let off the power to the axle when you want the diff lock to disengage. sometimes you have to step on the brake, or turn the tractor left and right a bit to get the pin to slip free of the friction. If the linkage is jammed for any reason. Free it UP! Make sure the spring return functions.

 

[nbryan]

Great idea I will have to try on my BX.



But since the treadle directional pedal is on the same side as the brake, it would be better if I had two right legs... But I am sure it can be done.



One thing that absolutely does not register with me, is the idea that the diff lock must be applied when the wheels are not moving. Cannot see how one could have much of a chance of getting a pin in a hole that way, even if there were multiple holes for the pin to fall into. Seems like the odds would be against it happening. Is one supposed to keep moving/stopping the wheels multiple times, and at each stop trying the diff lock, until it happens to find the hole?



Can someone set me straight on this?

I hit the diff lock pedal while gently easing forward. Press the diff pedal lightly down, move forward slowly, and once one tire moves enough relative to the other (the diff slips a bit) the locking pedal will complete it's down travel and engage the diff lock pin.
Again, if the lock lever doesn't engage right away, don't force it harder. Just stay lightly on it until a wheel breaks free and turns against the other wheel. It will then lock.
If the rear tires are both gripping well, it may never lock.


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[Henro]

Okay, I think what I am hearing is what my common sense has told me all along, for the most part anyway.

In my mind, to get the Diff Lock to work one tire would have to be turning relative to the other, either faster than the other if both were turning (probably dangerous to try it then on a BX or B), OR very slowly if one tire was slipping and the other tire was motionless.

If one tire were motionless it would advisable that the rotating tire be turning VERY slowly. But it MUST be turning so the hole will come around and the pin can drop in it, right?

So I am wondering where the statement that "The Diff Lock must be engaged when the tires are not turning." came/comes from?

At this moment I almost feel like I dreamed that statement up, but I am sure I have seen it repeated many times either here or on TBN.

 

[nbryan]

There you have it. It says if one of the rear wheels should slip, step on the diff lock pedal.
It also says do not engage diff lock when one wheel is spinning and the other is completely stopped.
So with both wheels turning, and one wheel slips, press diff lock pedal until lock engages.
At least that's what I get from reading the manual. Actual practice is tricky, it seems.

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[Henro]

No doubt these instructions are confusing.

Perhaps someone can explain the difference between:

(1) When one wheel is stopped and the other is turning slowly, and

(2) When one wheel is turning faster and the other is turning slower?

Just seems to me like there would be no difference mechanically. But I don't really know what I am missing, if anything...

 

[nbryan]

No doubt these instructions are confusing.



Perhaps someone can explain the difference between:



(1) When one wheel is stopped and the other is turning slowly, and



(2) When one wheel is turning faster and the other is turning slower?



Just seems to me like there would be no difference mechanically. But I don't really know what I am missing, if anything...

I'm not 100% sure of the difference either. all I know is if the wheels aren't turning relative to each other the diff lock is difficult if not impossible to engage. It works for me if one wheel is stopped and the other begins to break loose, but I can see that if you are really loading the drive train and attempt to force the pin in under high power it may cause damage. But I am always very gentle on the drive pedal while engaging the lock.

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