4WD variations.?

[Schneeky]

.. I don't mean to hog the forum.. Hopefully someone else has the same questions that need answering..

.. Seems like I've heard or read somewhere that there's different kinds of 4WD available on tractors.. I know I've heard of a "forward assist" or some such.. Then there's that funky little thing on the Kubota's that knocks out the 4WD in tight turns..
.. What all kindof 4WD variations are there and are any of them to be avoided.? Thanks.!! d:^) Schneeky..

 

[Bob_Young]

This thread should bring some interesting information out of the woodwork.

In terms of design, I know there's the fully enclosed bevel gear drive system used by Kubota and the half-shaft from a central differential design used by everyone (?) else. The bevel gear system works really well...on small tractors at least. I have seen a few posts saying it's not the best choice for really large tractors and not as strong as the half-shaft designs. What they may really be saying is that the bevel gear front axles are more expensive for a given level of strength and, beyond a certain point, become cost prohibitive.

Don't know of anything on a Kubota that knocks out 4WD on a tight turn. Never seen it work that way on my own tractors; though I try to avoid turning tight while in 4WD.
Bob

 

[piller]

Kubota likes to point out that their enclosed bevel gear front axle drive systems deliver full power at all steering angles.

 

[roxynoodle]

My understanding is that all compact tractors use "front wheel assist" rather than true 4wd. At least I haven't seen a compact with true 4wd. A true 4wd will have the same size front tires as rear tires, like the Steigers do. We use the term "4wd" loosely to mean we can engage the front as well as the back.

 

[ericher69]

My understanding is that all compact tractors use "front wheel assist" rather than true 4wd. At least I haven't seen a compact with true 4wd. A true 4wd will have the same size front tires as rear tires, like the Steigers do. We use the term "4wd" loosely to mean we can engage the front as well as the back.

Not so! Tires can be different sizes and still be a "true" 4wd as long as it is geared properly.

 

[slewisma]

Not so! Tires can be different sizes and still be a "true" 4wd as long as it is geared properly.

The contact patch on those little front tires is a lot smaller than on the rears. So, if geared right, you can have full 4WD on anything but how much additional traction you'll experience is a separate question.

I can't speak for CUTs since I have a BX-24. I can say that on SCUTs, those front tires can sink the front to the frame in less time than it takes to realize you are getting stuck.

4WD is a very valuable feature for having four wheel braking through HST and it will probably be of some help in the winter on the driveway. In deep mud, not so helpful.

 

[IslandTractor]

Kubota likes to point out that their enclosed bevel gear front axle drive systems deliver full power at all steering angles.

What is the big deal about full power at all steering angles with a tractor? Full power and traction is typically needed when pulling a plow which is generally in a straight line or when loading the FEL bucket which is also a straightahead direction. When do you need full power/traction while turning hard with a tractor?

Seems to me this is just a marketing gimick.

 

[Schneeky]

..Hey IT, what do ya call that contraption on yer FEL there.? Looks like somethin I'd be interested in..
Will it go in place of a regular bucket or are there some additional hydraulics needed.? Thanks..

..Look Gizmo.. It's starting already.. Dang.!! d:^) Schneeky..

 

[IslandTractor]

..Hey IT, what do ya call that contraption on yer FEL there.? Looks like somethin I'd be interested in..
Will it go in place of a regular bucket or are there some additional hydraulics needed.? Thanks..

..Look Gizmo.. It's starting already.. Dang.!! d:^) Schneeky..

It is a grapple. do a search and you will find hours of reading on the subject here on TBN.

Yes, you would need to run hydraulics to the grapple. Several options. Again, do a search on diverter valve or rear remote and grapple. There is lots of info here on TBN on these subjects.

 

[stevem5215]

I have a Steiner 4wd Hydro tractor and it's a true system of 4wd. You can have wheel(s) in the air and they still only turn as fast as the ones on the ground. It's one h*ll of a machine for snow removal with the mini bucket (4ft) on it. I've never seen a tractor that can push a 3 foot pile of snow in front of the bucket UP a hill around a bend and pushing it in the direction you want to go. It's unbelieveable awesome. Also, this past winter I was plowing with it and went to take the trash can up the hill. It turned out there was ice under the snow and I could barely stand on the driveway on the slope. But it was weird that the Steiner could clear that snow without issues where I couldn't even walk. Just goes to show when engineering is applied to a solution what can be done.

Steve
Ford 1900 4wd & Steiner 420

 

[MarkV]

My understanding has always been like Roxynoodle that in the tractor world 4 wheel drive tractors have equal size tires on all four corners. Everything else I have ever seen has been called/considered front wheel assist.

MarkV

 

[DGS]

I guess it all depends on the way you look at it
If all 4 wheels are being powered then it's four wheel drive
DGS

 

[mwb]

What is the big deal about full power at all steering angles with a tractor? Full power and traction is typically needed when pulling a plow which is generally in a straight line or when loading the FEL bucket which is also a straightahead direction. When do you need full power/traction while turning hard with a tractor?

Seems to me this is just a marketing gimick.

For "doing doughnuts"

As far as I am concerned my Montana has 4wd (not "front wheel assist", whatever that is suposed to be). It does have a locking rear diff, no lock on front - so by definition it is really a 3wd
What is front assist? Does it have a rubber driveshaft?

 

[Gary Fowler]

My understanding or maybe misunderstanding of what constituted 4 wheel drive versus 4 wheel assist is that if it has a driveshaft to the front wheels then it was 4 wheel drive. If it had hydraulic motors assisting the front wheels, then it was that 4 wheel assist. Wheel size is not an issue

 

[MtnViewRanch]

I may be wrong about this, but I think that if you can shift your tractor in and out of four wheel drive, then it is considered to be four wheel assist. To be considered true four wheel drive, the tractor is in 4x4 mode all of the time and there is no option of in or out of that 4x4 mode. This usually applies to larger higher horse power tractors that are most often seen with the same size tires on all four corners.

Just my understanding of this common question.

 

[Timber]

I may be wrong about this, but I think that if you can shift your tractor in and out of four wheel drive, then it is considered to be four wheel assist. To be considered true four wheel drive, the tractor is in 4x4 mode all of the time and there is no option of in or out of that 4x4 mode. This usually applies to larger higher horse power tractors that are most often seen with the same size tires on all four corners.

Just my understanding of this common question.

That is called a Quadratrack. 4 wheel assist is not found in Tractors that I know of. 4 wheel assist would be more like the limited slip 4 wheel drive Auto mode that a lot of high end pickup trucks have, You also see it in sports cars like your BMWs & Audi's. Basically a 4 wheel assist would be found in a high speed 4 wheel drive for cornering and performance. A limited slip 4 wheel drive is what most of us are familiar with in our pickups and tractors, Tractors having the bonus of a differential lock.

 

[patrick_g]

My three trucks were all sold as 4wd, NOT ASSIST. They can all be shifted back and forth between 2wd and 4wd.

My tractor was sold as 4wd. It too can be shifted back and forth between 2wd and 4wd.

My trucks all have some form of limited slip/positraction on the rear but not in front.

My tractor has a manually operated diff lock on the rear but not the front.

I believe most folks would agree that my trucks are 4wd.

Why don't they agree that my tractor is 4wd?

The tractor is a Kubota with the "controversial" bevel gear design. It hobby horses (bounces fore and aft and up and down) when turned sharply in 4wd. I try to avoid that but... sometimes it is easier to endure it than to shift out of 4wd to turn and back into 4wd again to work.

Tight turns in 4wd tend to tear the surface a lot more than in 2wd.

Oh, and of course equal size tires front and rear is NOT a requirement for 4wd and in smaller tractors is not usually desirable. I'm not knocking anyone's equal size tired machine which may do some limited number of chores fantastically better than the "normal" configuration. I'm just saying there are good reasons why CUTS are typically carrying smaller tires up front.

Pat

 

[TheFlatlander]

I agree with Pat on this. Good post.

 

[rtimgray]

I really think that it is a combination of old and new terminology. Back in the day, when MFWD/FWA/etc. small tractors were rare, the only four wheel drive tractors around were the large articulated tractors, with front and rear tires of equal size. These were, and still are, the four wheel drive tractors.

Since we have entered an new era in tractoring, and the advantages of added front wheel assist to small tractors far outweighed the cost and have become popular, the term gets a little fuzzy. I believe there was a time when John Deere, and maybe others, added hydraulic powered front wheels, for a true front wheel assist, but it was never intended to be used as such for an ongoing basis (like use it only to get through a sticky spot).

After that, the MFWD (mechanical front wheel drive) term came about to distinguish these tractors that had an actual driveshaft going to the front axle as opposed to those that used hydraulic drive.

Since then, I think that these terms have confused the casual CUT buyer, but everybody understands what a 4WD truck is. So in sales literature and seller to buyer conversation, even now the little tractors that have mechanical front wheel drive are called four wheel drive (I think mine even has stickers on it saying 4WD).

Now, are our little tractors with mechanical front wheel drive true 4WD - well, sorta. They have the capability to transmit power to all four wheels, but may not all the time (or may not part of the time due to lack of a differential lock in the front and/or rear). In the grand scheme of tractors past and tractors future, the little tractors with MFWD will probably continue to be called 4wd just so folks don't confuse them with 2wd (I guess). Of course, I had a Belarus 420 that was 4wd of some sort - but it had a viscous coupling and it decided when to power the front wheels. You could not shift it in and out of 4wd. If the back wheels overspeed the front by too much, it was engage the front (and it worked well climbing hills and using the loader). So I don't really know what version of MFWD/4wd that was.

As far as I am aware, a Quadratrac is either a type of transfer case used in 4WD trucks/SUVs/Jeeps, or the Case-IH designation for the type of tractor or tracked tractor with equal front and rear tire sizes. For a long time around here, whenever anyone talked about that type of tractor, it was a Steiger, no matter if it was a Case, John Deere, New Holland, whatever. I would guess it is a regional dialect type thing.

In conclusion, if your tractor can engage power to the front axle, and you want to call it four wheel drive, I don't think your wrong.

 

[patrick_g]

I really think that it is a combination of old and new terminology.

In conclusion, if your tractor can engage power to the front axle, and you want to call it four wheel drive, I don't think your wrong.

I agree that some folks are not up to date terminology wise and create confusion when communicating with those of us who are.

So are our trucks really just front wheel assist? I don't think so.

When you engage 4wd you power all the wheels, in many cases in CUT's, mechanically. Whether or not there is sufficient traction to prevent wheel slip at some particular HP output is another matter. So limited slip or not in the rear and like wise in the front is not really the issue just as tire size is irrelevant.

CUT's are intended for extended periods of 4wd as needed and determined by the operator as are pickups. It is, at best, inconsistent to call a truck with a transfer case and a drive shaft that can power the front differential a 4wd truck if the same, nearly the same, or equivalent mechanical configuration on a tractor is not 4wd WITH NO EQUIVOCATION.

I have no problem with the technologically out of date folks using their antiquated terminology. Shucks, I have to be careful to not say ice box and other anachronistic terms. My problem is with those who insist that those of us trained on new technology and terminology are wrong, misguided, or at best marginally tolerated. If a finer distinction is needed to differentiate between styles of achieving 4wd then that too is another issue but so far has not been a hindrance in communications.

Pat