Differential...when to use.....?

[TSMART]

Not too sure when to use differential. Is that the same as posi-traction. I havent yet had a situation that I couldnt get out of in 4WD..of course I am a newbie on the subject. Would I go to differential lock if I am spinning all 4 wheels? (which hasn't happened to me yet either)...just curious. Any cautions or concerns when using differential??

 

[beenthere]

Stop spinning before locking the differential. You may cause some damage if you lock it in while the wheels are spinning (as usually both wheels are not in sync and spinning the same).

Also, you can't be spinning 'all four' wheels. The differential lock will tie the rear two together, but not the front two.

 

[greg_g]

Actually it's best if there's rotation for the diff lock fork to fit over the axle spline. Not spinning at full throttle of course, but just enough to get the fork to engage the spline. A quarter to half revolution of one rear wheel - while maintaining pressure on the lever - should be enough to engage. Let go of the lever. When you're unstuck, back off on the throttle and coast. Spring tension should make it disengage by itself. And you can use diff lock regardless of whether or not you're in 2wd or 4wd.

But no, it's not like positraction because there are no clutches. You should disengage diff lock as soon as you become "unstuck", and always move in a straight line. If you hit solid ground and turn the steering wheel with the diff lock engaged, the faster turning speed of the outside wheel puts undue stress on everything that's connected to it.

/greg//

 

[RonMar]

The only time I use mine is in mud or when on rough ground where opposite wheels(right front/left rear) have all the weight such as traveling diagionally over large deep ruts. In this case, the front and rear diffs will allow the other wheels to spin. Rear Difflock solves this problem and allows the tractor to move off this rough spot.

As Greg mentioned, the claw assembly on the Jinma's is square toothed(same as the 4WD claw) and usually requires some difference in rotation to come into alignment and engage. In the above situations, I am in low or creeper gear and with the clutch out and engine just above idle with one of the rear wheels rotating at a slow RPM, I hold pressure down on the difflock lever. At somepoint the claw will align and the lever will go nearly to the floor. When I no longer need the difflock, I lift the lever and hold it up with the back of my right leg. At some point shortly after that, the claw will dissengage and that will hold the lever up by itself. I can usually hear/feel it when the plunger pops out and smacks the end of the lever. The disengage mechanism is purely by spring pressure so a little bit of wheel rotation may be required for the load to come off the claw and allow the spring force to retract it. When new, the plunger/spring on my 284 was stiff and didn't want to disengage. It took using it a few times before it would pop back out reliably. You can tell it is still engaged because the lever will not stay in the up/disengaged position by itself.

 

[Trev]

To be perfectly honest, I have rarely found a situation where the diff lock helps in the least. (JD4300, manual tranny, R4 tires.)

I can see that, yes, both tires are now spinning uselessly as opposed to just one of them.. but I've yet to notice if makes a difference. If you are in enough trouble that one huge R4 cannot move you, my experience is that two won't move you either.

I know.. it doesn't sound like it makes sense.. but that's been my personal experience.

Bob

 

[3RRL]

</font><font color="blue" class="small">( To be perfectly honest, I have rarely found a situation where the diff lock helps in the least.)</font>

I have...
While doing some off road work, I got the tractor wedged so that one rear was up against a rock and the other was spinning without traction. Same with the fronts. I engaged the differential lock and the one that was against the rock crawled right over it.

</font><font color="blue" class="small">( I can see that, yes, both tires are now spinning uselessly as opposed to just one of them.. but I've yet to notice if makes a difference. If you are in enough trouble that one huge R4 cannot move you, my experience is that two won't move you either.)</font>

That's true for a "high centered" situation, or you are in so much mud and slippery stuff that 10wd wouldn't help. /forums/images/graemlins/grin.gif
But for situations as described above, it works.

 

[Trev]

Yes, you're right.. 10wd wouldn't have helped me at that point.. I had to hook a come-along to a tree to get out of that one. I agree that diff lock can help.. it's just been surprising to me how *little* it helped in the situations I've been in. In this case, I was in mud, with R4's, and the R4's just loaded up with mud so I basically had drag-racing slicks on the back. /forums/images/graemlins/smile.gif

I'm sure I'll find a use for the diff lock someday, and be real glad I have it!

Bob

 

[Soundguy]

</font><font color="blue" class="small">( I have rarely found a situation where the diff lock helps in the least )</font>

Occasionally when discing in less than optimum conditions I've needed diffy lock..

Soundguy

 

[corey]

RonMar,

Appreciate your description of technique for engaging and disengaging the differential lock.
I've used the differential lock twice on my 284LE and was concerned about not forcing the lever to engage. When the lever is pulled up out of engage your "use the right leg to hold" will be useful.

Did you develop the technique on your own or is it written in the manual ?

thanks,
corey

 

[RonMar]

"Did you develop the technique on your own or is it written in the manual ?"

On my own... At least I don't recall seeing anything written in the manual about rotation when engageing/disengaging difflock or 4WD other than not to use them on hard surfaces and difflock restricting the tractors ability to turn.

As to the procedure I use, If you look at the exploded views of the rear diff and transfer case, you can see the 3 tooth "Claw" assemblies. You can also see the 4WD Claw fairly easilly by removing the creeper case cover. They are straight cut and each piece is hard shafted to fixed components in the transmission, even when the clutch is in. There are only 3 points per revolution where they are going to be in alignment and with square/flat faced teeth, they have to be in alignment to engage. This design requires there to be some difference in rotation so the teeth will come into alignment and allow engagement(unless you are lucky and the teeth happen to be in alignment.

As for holding the lever with my leg, Since the lever won't stay up on it's own untill the difflock disengages and the lever stands behind my right leg, it seemd like the natural thing to do /forums/images/graemlins/smile.gif