2wd Always?

[john_bud]

That's speculation. I've seen all sorts of things damaged on used tractors. I'd suspect abuse or poor quality before I'd suspect that it was due to a 4wd tractor spending its life in 4wd. I'm not sure why folks can't understand that a 4wd tractor is made to spend its life in 4wd!

I'm personally glad that I don't waste any time wondering if or when I need to be in 4wd and the only time I do waste on the issue.....is here.

N80 - you may not notice the difference in turning radius as your tractor's turning radius is pretty tight. A 5% difference (on firm ground) is about 1/2 foot or less. If you are doing it on soft ground (fresh plowed), 4wd may turn tighter as the tires won't understeer and slide. That sliding is why single rib ag tires are used on the front of 2wd tractors, the rib acts like the keel of a sail boat and grabs to help it turn on soft soils. SPYDERLK pointed out the action of the front tires as there is a tight turn. One side MUST travel farther than the other side.


As you wrote, the tractor is designed with the front's turning slightly (normal range is 5 +/-3%) faster than the rear tires. Run in 4wd on dry asphalt or cement and the front tires will be skidding that 5% every revolution. It's the physics thing, that's where the least resistance is, so that's where the sliding occurs. That is the same as slamming on the brake and skidding 5-7" every rotation of the front tire. Actually, it's more like pealing out and burning rubber as they are overdriven... still it takes energy to do that.


If you read my note closely, you saw that the differences are small. Significant over long time periods and in fleet numbers, but not enought to be a bother.

Enjoy the tractor whether it's in 2wd, 4wd or in 22nd century hover mode!

jb

 

[D7E]

That sounds like speculation too and I'm sure the answer is system specific. Large ag tractors often have little in common with small utility and CUTs. And I wouldn't own a tractor that did that (unless there was a full time override) since that sort of behavior could get you killed on a wet muddy hill.

As far as fuel savings, some owner's manuals say specifically that 4wd is more efficient, though mine does not. An example has already been given above.

I do think people confuse modern CUT 4wd systems with the older automotive systems they are used to.

Have any of you put over 10'000 hours on a tractor as we do ...????
And these things make a difference....Stock farmers tractors (4wd all time) and (loaders) Always breaking up axles .
Grain farm tractors are expected to run to 15000 hrs (Only use fwd when neccessary)and rareley give problems ...I had 3 years with "NH" It aint speculation...?
Stock farmers that use the 4wd full time rebuild axles far more often..
The difference is obvious..Should the rules be different for smaller tractors ,Is there a difference in quality ,What is the life span of a cut ,Size for size you spend more money than we do.....?

 

[billbill1]

I leave black tire marks on my concrete if I leave the tractor in 4wd. If the ground is soft, I run in 4wd because I get lots less damage (ruts) than in 2wd. I use 2wd anytime I can to save wear and tear but as far as fuel usage, I see no difference. 4wd should never be used on pavement , unless there is snow and ice to allow for wheel slipage to the fronts. That's how I do it anyway.

 

[Egon]

For some of us using four wheel drive is not an option.

On my Kubota B7100 HST with a loader and no rear weight It's required to get the tractor up the slopes I work on. A rear weight is not really an option as I transport the the tractor on a regular basis. In town room is an issue and the less sticking out the back the better. On the Farm it`s not an option either as many times the tractor goes up the hills empty but comes back down dragging something.

Just for interest many years ago I was told that the optimum slippage for tires that are pulling is 10 %

 

[Ridgewalker]

For some of us using four wheel drive is not an option.

On my Kubota B7100 HST with a loader and no rear weight It's required to get the tractor up the slopes I work on. A rear weight is not really an option as I transport the the tractor on a regular basis. In town room is an issue and the less sticking out the back the better. On the Farm it`s not an option either as many times the tractor goes up the hills empty but comes back down dragging something.

Just for interest many years ago I was told that the optimum slippage for tires that are pulling is 10 %

Egon, you should consider filling your tires...weight in the back is a good thing, especially when you have a FEL.

As to the OP, I am in the use 4WD only when you need it camp. I can tell a difference when in 4WD vs 2WD when making turns, etc.

 

[N80]

N80 - you may not notice the difference in turning radius as your tractor's turning radius is pretty tight. A 5% difference (on firm ground) is about 1/2 foot or less.

Actually it would be more than that. The tractor has a turning radius of about 10' but that's using a brake. So its wider than 10' and whoever quoted 5% actually said 5-10% which could put the difference as high as 1.5'. Which still isn't much, and in general practice might not be noticeable. Which begs the question: If we're going to say that .5-1.5' is trivial, then doesn't that just support my basic contention that the difference between turning in 2wd vs 4wd is insignificant?

But yes, I did claim there was no difference with my tractor...so let's go back to that point. I've stated several times but some folks seem to ignore it or disbelieve it, but I tested this. It was on firm ground at slow speed. At a stop I turned the wheels full right in 2wd. Start driving and stop halfway through the turn. Mark outside diameter. Complete turn. Mark outside diameter. Do it again in 4wd. No difference. What can I say? Could I be off by a few inches? Sure...in either direction.

As you wrote, the tractor is designed with the front's turning slightly (normal range is 5 +/-3%) faster than the rear tires. Run in 4wd on dry asphalt or cement and the front tires will be skidding that 5% every revolution. It's the physics thing, that's where the least resistance is, so that's where the sliding occurs. That is the same as slamming on the brake and skidding 5-7" every rotation of the front tire.

I don't think anyone here has advocated running 4wd on pavement. Even the 'always in 4wd folks' take it out for pavement. Its just common sense and is part of our theory of leave it in 4wd until you need 2wd. The beauty of which is that we don't have to spend much, if any time wondering when we need to switch it into 4wd and we are much less likely to find ourselves in need of 4wd.....when it is too late.

 

[N80]

Should the rules be different for smaller tractors

Of course! That's my whole point. Everything is different! Size, weight, usage patterns, 4wd systems, HST's, all that. How many of these big Ag machines you're talking about have bevel gear front drive systems? I doubt such a system is applicable to big heavy machines.

 

[Egon]

Filling the rear tires is not an option as the tractor is trailered on a very regular basis.

Yes, I know I should have weight on the back when doing loader work and many times that is what my back blade is doing. But it is unsuitable as a regular weight due to size and lifting ergonomics.

I also need four wheel drive to rota-till.

On the larger agricultural equipment I can't comment due to lack of knowledge but there are many industrial front end loaders that are constant four wheel drive.

 

[SPYDERLK]

If we're going to say that .5-1.5' is trivial, then doesn't that just support my basic contention that the difference between turning in 2wd vs 4wd is insignificant?

But yes, I did claim there was no difference with my tractor...so let's go back to that point. I've stated several times but some folks seem to ignore it or disbelieve it, but I tested this. It was on firm ground at slow speed. At a stop I turned the wheels full right in 2wd. Start driving and stop halfway through the turn. Mark outside diameter. Complete turn. Mark outside diameter. Do it again in 4wd. No difference. What can I say? Could I be off by a few inches? Sure...in either direction.

Good test. I see you did it slowly and that is a wise choice. There is still an issue with making a stop while turning in 2wd. There is a small outward step in the path as you restart. Starting slowly minimizes this, but slowly is a relative term and so leaving out the stop variable entirely is better still.

We can leave out the measurement variable too. Try this: [Go around the circle at your steady slow speed in 4wd. Then without stopping flip the lever to 2wd while watching the front wheels carefully.] It is likely, almost assured, that there will be some resistance to operating the lever, and that when 4wd disengages the front of the tractor will slew somewhat toward the center of the circle. This is how my BX1500 acts and its driveline is just yours in miniature I think. All three of my Kubotas act this way and Im sure the Mahindra would too, but opposing forces in the linked gearing are too great for me to operate the lever to disengage it.

Whether a difference is insignificant will be relative to the use. An advantage in maneuverability, however slight, becomes less and less insignificant as constrained repetition of movement is required. Your point of having it in 4wd when you need it is well taken. It is a risk not to do the same thing everytime, but the risk is not so much in judgement as it is in forgetting to put it back in 4wd when you are finished with the situation that 2wd provided the benefit. The weighting in the cost vs benefit equation remains personal.

You mentioned that we are wasting time with this. I view it as an opportunity to learn. Your tractor is exhibiting operation in a manner different than any I have encountered. Learning why has value to me.
larry

 

[SPYDERLK]

Filling the rear tires is not an option as the tractor is trailered on a very regular basis.

Are you so close to the trailer weight limit that 200# or so would be critical to trailering??
larry