I heard of the on demand 4x4, by sensing rear wheel spin. My questions are
1) How does this system provide true diff lock to the front?
2) Why is there a switch to go in and out of 4x4 if it is auto sensing?
Thanks
P.S. I am talking about the 2002 models.

 

How I understand it. I may be off a little or a lot:

The front hubs are semi-engaged by a electrical magnetic clutch. When either of the front wheels spin 1/5 less than the rear the front hub for that wheel fully engages, hence true 4x4. When the 4x4 is turned on and the atv is turning, the inner front wheel hub is locked since it is spinning less that the rear wheels. This causes the steering to be tough. I guess the switch is there to alleviate this and the unnecessary drag on the engine when 4x4 is not needed.

 

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I only use my 4WD when it's extremely muddy or to get out of holes or to climb a hill.

90% of the time I leave it in the "off" position and just ride as if it were a 2WD quad!

 

All I have to say is watch other 4x4's go through mud...I like to call them 3 wheel drive. Polaris pulls evenly with every wheel when 4x4 is engaged. The reason for being able to turn it off is say you want the rears to throw a couple rooster tail...well then magically the fronts snap into action and buck you, or make trail riding hard on the arms for turning...very unpleasant. So polaris' 4x4 is strong as an ox when you need it and stays outta the way when you want to play!!

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00 scrambler 400 4x4 K&N
98 xplorer 400 K&N, boysen reeds, clutch spring

 

front diffs on polaris are spool style . both front axles are pulling all the time they engage the hubs via a roller clutch it locks one way and freewheels the other. anytime the axle is moving faster than the wheel this hub engages. this is why polaris atvs dont tend to flip on downhills like all other atvs. there is a spring that keeps the roller clutch inactive and when you flip the AWD switch there is a coil around this clutch that creates a magnetic field that in turn allows this roller clutch to become active when rear wheels spin. on some 2002 models this feature has been moved inside the diff. maybe this will help you guys thanks nick

 

Thanks guys. Where on the net can I get a good read up on this?

 

Hope this helps.With the Polaris All Wheel Drive System activated (AWD selected), the machine operates as a 2-wheel drive vehicle until the rear wheels loose traction. If the rear wheels loose traction the front wheel rotational speed will decrease, causing the front drive axle speed to exceed front wheel speed. Restricting the rotation of the drive clutch of the roller cage will cause the rollers to climb the ramps of the cam, and become squeezed between the ramps and the ring in the hub. When the hub clutch assembly, wheel hub, and drive axle are engaged, the front wheels will drive and engaged until rear wheel traction is regained. When traction is regained, the front wheels will overdrive the hub clutch, pushing the clutch rollers toward the lower part of the cam, disengaging the clutch. The rollers are held in place by the spring. The tension of this spring is critical to AWD hub operation.

It is important that the front and rear axle drive ratio and tire size are not changed. Changing this ratio will cause erratic engagement.

When AWD is selected in a forward gear, current flows through a coil of wire located in the strut housing, creating a magnetic field. An armature plate coupled to the roller cage is attracted to the magnetic field, and resists rotation, creating drag on the drive roller cage assembly. This causes the roller to climb the ramps of the cam, engaging the hub. Note: In reverse gear the override button must be pushed to deliver power to the wheel coil.

 

ck your factory manual