Ok, I keep reading about this 3WD vs 4WD and I would like to clear up this missunderstanding.

Differentials are a unique design setup allowing both wheels to be powered at the same time, but changing the gearing to each wheel as the vehicle is turned. Both Wheels have equal "driving force" hence 2WD. Cars have had this set up for many years. (ever burn rubber in a car and see two black marks?) The reason for a diff is when turning, the lengths of the tacking varies. The inside wheel travels less than the outside wheel.

Without a differencial,(solid axle) one of these two wheels will have to slip to make up this difference in wheel tracking/travel.

What happens is, when one wheel looses traction, the power transfer is shifted to the wheel loosing the traction. Result is, the non-traction wheel doesn't pull,but spins freely and traction wheel doesn't pull.

What a Limited Slip Diff does is, it senses the speeding wheel.. and locks it's free wheeling. Power is then transfered to the wheel with traction. Now I guess this is where the myth of 3WD comes from.

What people are calling true 4WD is where the differential is locked, like a solid axle.

Now picture this, IF one wheel of this solid axle is off the ground, not making contact, is it pulling? NO. Is this not the same effect as what people are calling "3WD"? Ahh.. yes.

If all 4 wheels of a Limited slip differencial are on the ground, all 4 wheels are pulling.

The benifit of having a differencial in the front is improved steering. (no slipage in turns from varing wheel tracking).

I hope this clearafies this debate over 3wd vs 4wd. (There is really no such thing as a 3wd system)

Sorry if I got too technical, this was just bugging me and I felt I had to explain this.

 

Brian, I like it! I like it!

Question: What do you call a Polaris, AWD activated, both front hubs engaged, with one wheel in the air?

Answer: Three-wheel Drive!

(I'd use the word "restrains," instead of "locks," in your phrase, "locks it's free wheeling," because only a locker (e.g., Detroit Locker) actually "locks" the free wheel, but hey! I can bypass a nitpick for the fresh look at the situation you provide.)

In earlier discussions, some posters indicated they believed ALL differentials only powered ONE wheel, bringing up intersting questions: which one? Left or right? How do the boys at the factory decide? Odd and even, left and right, for days of the month? If only one wheel is powered, why provide two half-shafts? And so on, deeper and deeper into absurdity.

Again, thanks for sharing your perspective.

Tree Farmer

 

LOL TF!.. always a joy to read your post..

ok, different scenerio If AWD Polaris and one wheel off the ground = 3wd,
then.. what is it when you have a AWD Polaris flying off a jump with no wheels on the ground...zero wheel drive.. Or Fly Wheel Drive!..LOL.. just kidding

 

Brian, I think the 3WD phrase comes from atv'ers being stuck in the mud and seeing only one of the front wheels spinning (non traction wheel) or having one wheel in the air and spinning, but nothing happening to the wheel on the ground with the traction. Hence they observe it's not "4" wheels driving.

Honda claims to have come up with a better system this year that puts the torque to the traction wheel instead of the spinning wheel. Haven't read anything that has tested this system yet, but hope to. I think it's the Polaris/Suzuki/locker guys who have coined the 3WD phrase due to those systems having a different arrangement for the front differential. As I understand it all 3 may have better traction under some circumstances but at the expense of turning effort.

 

Good job Brian. One thing though, if the new "torque senseing differential" that both Honda and Bombardier has works as advertised, wouldn't that negate any advantage of the much touted "true 4wheel drive". I mean think about it, on either system, if one front wheel is off the ground it will get no traction. Does it really matter if that wheel is spinning or not? When all four wheels are on the ground, all four wheels will be pulling. If spinning a wheel that is air born is an advantage, I guess "true 4wheel drive" has the advantage.

 

I only know what I have seen with my own eyes,my friend has KODIAK with limited slip.I have seen him with one wheel in the air spinning(on solid ground not mud)and other front tire doing nothing.In my opinion that is 3 wheel drive.I can get one wheel down and and have my polaris awd drive pull me out.As in cars with 4x4 if one tire spins you lose traction on that side as side that spins gets all the power.Question If limited slip works so great,what is the need for lockers?If I have one wheel in the air and it spins but at same time other 3 are on ground and they are pulling isn't this AWD drive.Many times here in the moutains I have watched jeeps,one with lockers will always out perform one with factory 4x4.I'm not into all the technical mumbo jumbo but can tell you what I have seen first hand,the proof is in the pudding.AWD is as name implys AWD.LATER COB

 

I think Wannabee explains what goes on most of the time with the expression ''3wd''.Most of us ATVers see someone stuck with one wheel in the air and spinning uselessly.That is certainly where that term comes from.Randomly ask 100 ATVers what the term ''3WD'' means to them?90% will tell you the above.Are we getting to ''TECHNICAL'' with this term?===BILL

 

Consider this situation:

An automobile.

Say a Ford Crown Victoria; stock; like STOCK.

Has a differential (not limited-slip, no locker, no traction-assist).

Gets one rear wheel jacked up in the air.

Wheel in the air spins; wheel on the ground does nothing, Ford Crown Victoria goes NOWHERE!

Is the Ford Crown Victoria a ONE-WHEEL-DRIVE vehicle?

Why not? It has ONE differential; you call a quad with spooled rear wheels (two driving wheels) and one differential (one "driving" wheel), "three-wheel drive."

Now, consider another vehicle; Ford or Chevy or Dodge "4X4," pickup or SUV, with no trick differentials (no limited-slip, no locker, no traction-assist). These vehicles have at least two differentials, one front and one rear.

Jack up one side of the vehicle, so two wheels are off the ground. Give it the gas. Two wheels off the ground spin; two wheels in contact with the ground just sit there; "4X4" truck or SUV goes NOWHERE. Is the example pickup or SUV "TWO-WHEEL DRIVE?" Two differentials, two spinning wheels; why not, if a quad with a spinning differential-attached front wheel is a "THREE-WHEEL DRIVE" vehicle?

If a regular single differential passenger car is NOT a "one-wheel-drive" vehicle what is it? If a two-differntial "4X4" pickup or SUV is not a "two-wheel-drive" vehicle, what is it? I know some characterize a quad with spooled rear wheels and a front differential "three-wheel-drive," I'm looking for some consistency.

Tree Farmer

P.S. One more example comes to mind; the Kawasaki Bayou 300 "2WD."

Now, clearly, you consider the Bayou 300 4X4 a three-wheel drive machine; what about its similar companion, the Bayou 300 "2WD" model? The Bayou 300 has a locking rear differential (no front-wheel drive at all). When the Bayou 300's differential is unlocked, when one rear wheel is in the air, it spins; the wheel on the ground does nothing, and the Bayou 300 goes NOWHERE. Is the Bayou 300, with rear differential unlocked, a ONE-WHEEL-DRIVE machine? Why not? The 300 4X4 only gets credit for one "driving" wheel attached to its FRONT differential, why should the Bayou "2WD" get credit for two "driving" wheels attached to its differential?

T.F.

 

Chickenman you seem to get it! Yes a Polaris with 1 wheel off the ground still has 4 driven wheels.
read this again...
"what is it when you have a AWD Polaris flying off a jump with no wheels on the ground...zero wheel drive.. "
No it's not zero wheel drive, it's zero traction is what is! If it's zero wheel drive can anyone explain than what makes the wheels go around. They are being driven! Yes a Crown Vic with one wheel off the ground and spinning is 1 wheel drive. A car with a diff is called "single" trac after all...
As for the 4x4 thing with SUV's etc. The 4x4 thing is a great selling point for auto manufactures. But the fact is yes, most SUV's & trucks have diffs front & rear. So to get down to brass tacks, yes they are 2WD. So why not buy a regular 2WD truck then? Because it can only "push" (rear wheel drive) it can't push & pull (4WD). But to give auto manufactures the benefit of the doubt if all 4 wheels of an say Explorer have equal traction all 4 will spin even though there are diffs front & rear. Put the right side only in mud though & you may be stuck, or at least have to ride the brake to get out.
That's why Honda can claim 4x4. If all wheels have equal traction all 4 wheels will spin. 4WD!
If you put one wheel in the air and only have 3WD that is your problem for putting it in that position. If a Polaris has one wheel in the air it still spins. Even though it's not on the ground. So there is no way one could say that is 3WD! It's not a loss of drive, it's a loss of traction. Traction & friction is needed to propel yourself foward. Take my 5.0...please (no seriously) Say I hit the line locks and just sit & burn rubber, 2 fat *** 50 series Hoosier street slick black marks on the road. What was that? It was 2WD (posi rear end with an extra tight unit). It was not zero wheel drive because I wasn't moving! It was zero wheel traction! I mean how the hell did my interior just fill with smoke from the tires? Something was driving them! I just happen to turn the tires hard enough to overcome their traction.
c-ya,

 

Andrew, when you "burn rubber" with your awesomely powerful car, you do not "overcome" the force of fricion (nor traction entirely) between the surface of the strip (?) and the surface of the tires; the coefficient of sliding friction, under the conditions you describe, gives your car the tremendous acceleration you describe. Unquestionably, with both rear wheels laying those spectacular rubber marks down, each contributing its share toward the maximum of (rear wheel loading) X (coefficient of sliding friction) forward thrust, you describe two-wheel drive!

The coefficient of sliding friction is usually less than the coefficient of static friction.

If there were no friction between the strip surface and the tires, i.e., if you totally "overcame" friction and traction, your car would go nowhere (like a stock Crown Victoria with one wheel jacked up).

Tree Farmer