Tires spinning

   / Tires spinning #11  
JOHNTHOMAS said:
I know Kubota calls their tractor or my tractors 4wd and I've often times seen that only 2 of the tires would turn (spin in mud or on ice) when in 4wd unless I stepped on the locking differential which would then make 3 of the tires turn while one was still not moving.
Philip, what would you call that? I call it 3wd.:)
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It is still a 4wd tractor, okay, so you have 2 or 3 tires spinning, but is it always the same 2 or 3 tires that does the spinning? With open diffs front and rear, manually locking diff rear, when 4wd is engaged, all 4 tires are pulling equally until the torque of one tires exceeds the traction capabilities of the surface it is gripping. The open diff is designed so tires on the same axle can travel at different speeds, ie, turning a corner. Air locking diffs front and rear would solve problem, but would make it difficult to steer. My F250 is the same way, but I have a limited-slip diff in rear, which is probably worn out by now. Chevy and Dodge same as well. Just not noticed as much in trucks cause you cant see the tires! Philip.
 
   / Tires spinning #12  
Well, there is drive to all four wheels....just not at always the same time :laughing:

Cars and trucks are the same way except that many (most?) do not have the locking differential pedal.

But at least sometimes, having one front and one rear with power beats only have one rear with power:thumbsup:

The other big advantage of 4wd on a tractor (vs 2wd) is that it give you breaking on the fronts. Very important sometimes when going downhill!

Ken
 
   / Tires spinning #13  
k0ua said:
It is 4WD as long as the resistive/tractive forces are equal on a per axle basis. In other words, as long as the front tires have have the same load on them they will both turn. Same for the rear's. But if they are unequal on a per axle basis then it is possible to only turn one wheel/tire and the other to be stopped. I have seen many times when only 1 tire per axle is spinning, and many times when all 4 are spinning. If you use your rear differential lock you can guarantee 3 tires spinning .

James K0UA
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Philip, I think James explanation is perfect, but just assume you are not a mechanical person and you purchase your first 4wd tractor, you head out into a muddy field and get stuck and only two tires are spinning, do you still think it is 4wd? I have a quad that says 4wd and when I lock the front diff it is TRUE 4wd because it has no rear diff, is it tiring to drive like that, of course it is because it isn't practical to have a front AND rear diff locked all the time. Would I rather have a 4wd tractor/truck without locking diffs over a 2wd tractor/truck? 1000 out of 1000 times I would. I'm sorry if the way I proposed it offended you...
 
   / Tires spinning #14  
Tags said:
Philip, I think James explanation is perfect, but just assume you are not a mechanical person and you purchase your first 4wd tractor, you head out into a muddy field and get stuck and only two tires are spinning, do you still think it is 4wd? I have a quad that says 4wd and when I lock the front diff it is TRUE 4wd because it has no rear diff, is it tiring to drive like that, of course it is because it isn't practical to have a front AND rear diff locked all the time. Would I rather have a 4wd tractor/truck without locking diffs over a 2wd tractor/truck? 1000 out of 1000 times I would. I'm sorry if the way I proposed it offended you...
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No offenense taken, just trying to clear up an explanation for others that might be following. They are 4wd until the torque of one tire in a non-locking differtial exceeds the grip level of the surface it is operating on. Mainly happens to me when pulling a ground engaging implement in muddy soil or on ice. Philip.
 
   / Tires spinning
  • Thread Starter
#15  
Appreciative of all the great replies. This is a good forum. Tim
 
   / Tires spinning #16  
I have tried to explain how differentials work to many people, and usually without a lot of success, but I think that video explains it so well. Sure it does not cover lockers, air lockers, limited slips, spools or even the simple mechanical rear differential lock most of our tractors have on them. But it sure is a good foundation to move on to those subjects in my opinion. And yes I guess it is an eye opener to get stuck in the mud and maybe only see 2 wheels spinning, but hey it is better than just 1 wheel spinning... Been There, Done That..didn't like it much:laughing:

James K0UA
 
   / Tires spinning #17  
I agree good video. I wonder if I had seen it in school, but i probably dozed throught it or was watching girls lol Thanks for posting it. it really gave me insight into a differenctial, Even though I have changed a few gears in them over the years I never gave much thought to how they worked.
 
   / Tires spinning #20  
Well, a 2wd cor or tractor really only has as much traction as the lowest traction of one wheel.

A 4wd tractor has the traction of the 2 lowest value wheels.

A diff lock will add one more wheel to the above.

Pretty simple, really. Differential splits up the power to both wheels, either wheel on the axle can get any % of the available power.

--->Paul
 
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