A buddy of mine has an 04.5 500ho, he just installed an EPI clutch kit and in low it will carry the front wheels of the ground for as long as he can hold it there and after a certian speed the AWD kicks in while the tires are off the ground and it is in 2-wheel drive. Any one know what would cause this.

 

Not sure of exact design reasoning, but a friend of mine was doing donuts on ice in 2WD. Engine was at a very high RPM and all of a sudden the AWD kicked in. Next thing he knew, he was shopping around for a tranny.

 

Even though it's in 2 wheel it may sense the front wheels being stopped & will try to engage them??? I'm not sure.

Or the other thing that tends to happen on Polaris' is if the battery is very low the 4wd will act goofy.

 

has he changed the oil in it, if rusty or full of water it can cause it to enguage when spinning in 2wd, if it is always stuck in, pull out the front diff and open it up, probly got a broken hilliard cage..

 

popular to contary belief there is no speed sensing on a polaris four wheel drive. everytime i read magazine review i laugh at how the testers still don't get it. anybody who doesn't beleive this. take a polaris 4x4 and lift all four wheels of the ground in the shop and you will see that the back tires don't spin more than 1/5 of a turn before the front ones go. next time you out fourwheeling find yourself a ditch or a big log that gets you stuck when in two wheel. then push the button and try and go you will see what i mean. the system is on demand because you can push the button any time other than when the back wheels are spinning excessively, not because it will kick in only when needed. juat clearing up misconception. as for the problem hub fluid is good idea, a low battery or other electrical issues can cause the hubs to get voltage when you don't want. So if you are going really slow spining the back tires and it kicks in than i 'd look there. If you were going down the road at high speed and this happened it can be cause by a weak spring that holds the rollors into the hilliard cage. at high speeds you can over come the spring tension and the centripital force were cause them to activate.

 

centirigal force from the rear wheels at speed is causing the hillard clutch to engage and over ride the 4wd . basically its acting the same way as it would if you were stuck and locked the 4wd in and spun the rear tires

 

They do have a speed sensor its on the right front you can see the wire it runs down with the brake line, and 04.5 dont have locking hubs they lock at the diff.

 

Hello Toycrazy. The speed sensor is used by the speedometer to determine speed. mrtwostroke is right, the AWD is engaged mechanically. The other thing that helps the engagement is the electromagnet that attracts an armature that puts drag on the roll cage in the hillard. It is this drag that causes the rolls to jam between the output shafts and the ramps in the rig gear. Anything that can cause drag on the cage will engage the hillard. When you spin the rear tires on ice (or have the front in the air), the front tires are not moving. The large speed difference between the cage and the output shafts to the front wheels probably creates enough drag (remember oil drag) to engage the hillard. It has nothing to do with centrifigal force. Centrifigal force would actually tend to hold the cage out of engagement on the new machines with the hillard in the diff.

Now when you are driving down the road at high speed, you will not have this high speed difference, so the hillard will not engage.
I hope this helps,
Bryce

 

BTW.. the Polaris AWD typically kicks in in about 1/12th of a wheel rotation. This number has to do with the number of lands in the Hillard. We hashed this number out last year sometime in another thread. And it was verified with measurements. I think this 1/5th number comes from a mix up because of the difference in rotational speed between the rear and front tires of 20%. However, even this number is off, because Polaris has built machines that seem to vary from about 17% upto over 20%. Depending on the model.
Bryce

 

i'm not sure which one of you said it, but that little wire that goes down to the front hubs is for suppling voltage to the electro magnet. now the newer ones have a different system for reverse speed and power limiting. the old ones simply retarded the iginition and locked out the 4wd. the new ones lock out 4wd, but don't retard the iginition untill you pass a certain speed. If the spring that holds the rollers in the hilard breaks complete, it doesn't need any speed difference in order to engage. just enough centripetal force (yes that's centripetal force not centrifugul force. centrifugul force is an incorrect thoery that the net force in a spining object is toward the outside. if the net force is there what keeps the object moving on the circular path. sorry my old physics teacher was always ranting about that) to put the rollers to the outside. But now i'm going to correct myself, in my previous post I said that could not happen sitting still, but i'm wrong because even though you are sitting still and spinning the back tires, your front diff or eccentric and shafts are tuning as well as the hillard and cv joint the only thing not turning is the housing and front wheel. So ya if there is a broken or weak sping in the hub the front wheels will always want to engage. as for the new ones i haven't touched our 05 800. but that is interesting that the hillard is in the diff. but i bet it is still turning if your back wheels are so the same probably still holds true. well i've rambled on long enough good bye