there is not magic or voodoo or complicated theories
simple if the front axles accelerate faster than the front tires are turning the sprag or hillard locks!!!!
assuming the AWD switch is on and the coil is energized

jack up all 4 wheels and try it

 

Hello baxy. There is no confusion about how the AWD works, we were discussing why the front wheels may lock when the AWD is not on. It seems clear that the overunning clutches can only engage when there is drag on the armature plate or the roll cage. So we were talking about what could cause this drag when the AWD is not on. On the other hand, when the AWD is on, it is the difference in speed, not the acceleration that causes the overunning clutch to engage. And in this case, the drag on the armature plate caused by the coils being energized allows the clutch to engage.
Bryce

 

Thanks again for the replys. Am learning more than I expected on the physics. Still a bit fuzzy on what locks to what. I went to the Hillard web site, but that wasn't much help. I suppose this is something I'll pick up in time. I have jacked the bike up on stands and put it in gear with the AWD on. Light comes on. The rear wheels go, the front pretty much just sit there, but with occasional slight forward movement of the front wheels, moreso the left, not that that matters, I'd guess. Polaris shop manual says if lf light comes on in switch, (of AWD) then it is something mechanical, and to go to mechanical troubleshooting section--which I haven't found yet. Haven't had much luck with the Climber Manual either. Is this so? A friend of mine said not necessarily. Anyway, If it is mechanical, what wears out? The rollers? The hubs? Where exactly are the magnets? Inside the hub surrounding the axels? No dealers out here. Is the info on resistance, and where to check in the manual, or is this something more intuitive, cause I didn't see it in there. Maybe I'm just blind [img]i/expressions/face-icon-small-blush.gif[/img]

 

What causes the hubs to engage is the wedging of the rollers against the outer hub assembly. It SHOULD be caused by the coil inducing a magnetic field. But there are other forces that seen to make the rollers to lock up.

I used to think that the oil viscosity was the problem or at least the big contributor, but I now think it’s the minuscule particles of metal that floats in the oil that adds to the mass of the oil itself. These particles are magnetized eventually and when you add the centrifugal force of the oil spinning off the internal hub you have the POTENCIAL to cause the difference in speed that will cause the rollers to wedge in the hub assembly.

The lighter springs and lighter oils are all something that may help but and have been played with, but it’s a short term fix for a long term problem.

I don’t believe the “torque pulse” is being isolated by the belt. I believe it is being magnified by the belt or should I say the the cvt system that’s why transmissions were such a problem in early quads. I don’t think this surging causes the engagement as much as I believe it pounds the system by constantly micro engaging it in and out.

I think that’s why the Hilliard work so well on Electric motors. With their constant smooth rotation the rollers are held in place constantly and firmly.

 

To what do the rollers wedge? Is the inside of the outer hubs octagonal? I guess I need to tear into 'em again to get to know this system better. Do I just need to know if power is getting to the coils, or do I need resistance figures?

 

The rollers in the clutch jamb between the hexagonal driven axle and the inside of the wheel hub on your machine. However, this only happens when two additional things happen: first, the coils must be energized in the hub and secondly, the rear wheels must be spinning faster that the front.
What you should check now is if the coils are being energized in the front wheels. Two things to check. First is power being sent to the coils when the AWD light is on. Second, do the coils have a reasonable resistance. As has already been mentioned, you should have the proper hub oil and the hubs must be clean.
There aren't any magnets. The magnetic force is created by the coil.
Hopefully someone can help with the resistance readings of the coils.
Bryce

 

24 ohms resistance is spec between the gray and brown/white wires with infinite ohms (no connection) checking gray to ground.

Another thought is the spinning of the rear tires at a high rate of speed in 2wd may create enough centifugal force on the rollers to overcome the spring pressure and slammo, you get broken parts. I never thought it was wise to spin the rears excessively with this system for that reason......

 

If I read correctly you have a 93 not sure of that year but I think these readings are the same
hub coil,un plug it under the front hood, and put a multimeter on it. brown wire to grey wire 28 ohms. if open , broken wire, if higher reading, shot coil.

http://www.imageevent.com/gsimpson/fourbyfour

 

You maybe right that crude in the oil can cause drag on the armature to cause the clutch to engage, but I don't see that the particles in the oil will become magnetized to cause it to engage. Also, centrifical force plays little to nothing in the engagement of the clutch. There must be a simultaneous application of drag on the roll cage AND a significant speed difference (more than 15%). The reason for the speed difference is because there is a gearing difference of at least 15% between front and back. And this speed difference must be OVERRUN prior to engagement of the clutch. The clutch will only transfer torque from the drive train to the wheel. That can only happen when the drivetrain attempts to go faster than the front tires. That is the whole concept of an overunning clutch.
No, it effectively isolates the engine from the drivetrain.
It cannot micro-engage because the speed deviations from the engine torque pulse are not high enough ie: 15% change in speed. At 3000rpms, that would be equal to 450 rpms at the crank. An engine does not change by 450rpms at the crank due to torque pulses. At full throttle for a car engine, you might only see 50 rpms change. However, that change is dampened by the isolation of the torque springs in the clutch disc in a car, or the CVT belt/clutches in a quad. The 50 rpm change is reduced to only about 1 rpm at the trans. Now the transmission itself is an additional spring that pretty much wipes out any additional speed changes. By the time it gets to the front end, there is nothing.

Basically, the overunning clutch needs both a speed difference (greater than 15% betwen front/rear tires for the Polaris) and drag on the roll cage to engage. Without both, it will not engage.
Bryce

 

OK I got it: brown or brown/white to grey = 24 to 28 ohms. Zero = broken wire. Higher resistance = shot coil. Grey to ground should be infinite; any other reading means there's a short. I "had to" go buy a boat last night and wasn't able to work on the bike. I'll check it out this weekend and let you guys know. Thanks again.