Locking the AWD

[tekrsq]

I'm still learning how the AWD works on the wife's 05 Scrambler 500. BUT, if I understand it right, it is activated by sometype of armature that engages the front wheels when it detects the rear wheels spinning. Is this correct ???

If so, is there a way that I can "trick" the armature into thinking the rear wheels are spinning and "lock" the front wheels (for true 4wd) when I put it in AWD ???

Ideally, I'd like just to be able to have it operate as designed, but if I really needed true 4 wheel drive, I just flip a switch and it would lock the front.

Is this possible ?

[blueline15]

Yes, by installing new tires were the front tires are at least 20% bigger then the rear tires, you would be causing the machine to think the rear tires are always slipping. Basically, you would have to calculate the tire sizes out to were everytime the front tires goes one rotation around, the smaller rears would need to have gone 1.2 times around in the same distance traveled.

I do not recommend doing this what so ever. But it is how you would do it

[SMP63]

Sounds to me like a good way to tear up the drive train!

[blueline15]

Yes, it's very bad. It will feel like and maneuver as good as an army tank would, and it will destroy tires, axles, CV joints, your shoulders/arms, and the roller cage very fast.

You will probably be wrenching on this machine an hour for every 15 minutes you ride it. I would buy stock in the companies that make the tires and driveline components, and buy these parts in bulk as much as you can.

[tekrsq]

I'm not looking to do it this way. I don't want it to always be locked in 4wd becasue of everything already said. I just need a way to lock the front for the ocassional occurancethat I need the front tires to help pull the machine in a straight line.

I assume the front drive system works off of some type of resistance readings that are sent to the armature to signal it to activate. If I could figure out how to tap into that, and how much resistance I need to give it to make it think the rear is slipping, then that might work for what I need. I'm just not familiar enough with these machines to know where and what to tap.

[blueline15]

it doesn't work like that, which means you really can't lock the front in unless you run different sized tires. With the switch off though, and different sized tires, it shouldn't engage.

When you hit the awd switch, it sends a voltage to the front gearcase, and this basically puts the front gearcase in an "overrunning" mode. Everything is geared so that the fronts want to turn 20% slower then the rears. So as long as the rears have traction, the fronts are being "overrun" and don't engage. When the rears slip that 20% wheelspin, the front now kicks in a locked position and helps pulls the machine through. As soon as the rears regain traction and begin to push through the front tires, they will disengage again until they loose the the resistance of the rears pushing on the fronts.

That's basically how it works. The entire engagement is purly mechanical, all the switch does is power a magnet that attracts the armature plate so the front wheels will engaged. That is what puts the front into it's "overran" mode and from there, it waits until it looses the resistance of the rears pushing to engage.

Which is why you would need to put smaller tires on the rear, or bigger tires on the front to lock it in. There is nothing you could do electrical wise to lock it in.

Also, realize that when the AWD kicks in, both front wheels are locked and pulling together just like a locked front differential on any vehicle with a limited slip. The front is already locked in just like you are wanting, as long as it is working properly. It is a true 4x4. The beauty is it will disengage when not needed to make steering easy and reduce drivetrain componet wear.

[Gear_Head]

Originally Posted by blueline15

The beauty is it will disengage when not needed to make steering easy and reduce drivetrain componet wear.

It is a great system, love how you can steer but have the true 4x4 only a wheel slip away.

[mstermechanic907]

this 4x4 system is a true 4x4 system it is based off truck 4x4 with their hilliard locking clutch front differential,once the 4x4 enguages it stays enguaged until you let off the gas and really slow down.this is a true locking differential,if you get one front wheel off the ground you still have three wheels driving.not like the limmited slip differentials on some brands.when in 4x4 just punch it and you will be in 4x4 and pull in a strait line.

[tekrsq]

Thanks blueline !!!

Well, since it doesn't work like I thought, I'll have to think about this a bit. Like I said, I do not want it completely locked all the time when it's in AWD. I like the way it works now (and so does the wife), but I have found some situations where having the front totally locked would REALLY have been helpful.

Is there a way to test the front drive to see if it is completely engaging as designed ?

[blueline15]

I think you should be able to put it up on jack stands with the AWD engage, and all 4 tires should turn.

Here is a video to kinda show what is going on. This machine has the exact same AWD system as yours.

‪Polaris AWD demonstration‬‏ - YouTube

‪Polaris AWD demonstration‬‏ - YouTube

Also, maybe this might be something might be looking for. A much less permenate way to lock the front. They call it "wedging" the front

I wrote to Matt Cowen, the Engineering Product Manager at Hilliard Corporation and asked a few questions about the Hilliard Overrunning Clutch used in the Sportsman ATV's.

First my questions, followed by the response from Hilliard with their permission to share the information:

1) I regularly engage the AWD clutch for 4-wheel engine braking by causing the rear wheels to slip in reverse, stopping, then putting the machine in forward before descending the hill. Will this harm the clutch at all?

2) When I perform the above maneuver the clutch remains engaged, even while powering forward, until I switch off the AWD engaging coil. Is this normal operation for the clutch?

3) Is there a way to engage the clutch prior to wheel-spin, allowing me on-demand AWD?

----

Mr. Anderson,

The condition that you are asking about above is called "wedging". What you are doing is locking the rolls in the reverse profile of the clutch (it is a bi-directional clutch set-up) and proceeding in the forward direction thus not allowing the clutch to overrun (which is the normal condition). This in turn locks up the drive train and makes the system steer like a fully locked differential. This condition is

Advantageous if going down a steep hill because it will only allow the front wheels to move as fast as the drive train. This will fully utilize the engine brake because when going downhill the weight distribution of the bike goes to the front end and that is where you want the majority of your traction.


This "wedging" will not hurt the front gear case, but it could accelerate the wear of the the drive train components (such as the front prop shaft) because it does completely bind up the system and the bike

will be very difficult to steer. Because of the binding and additional steering effort, neither Hilliard nor Polaris will recommend doing this.


You can get the system out of the "wedging" condition without turning the power off to the AWD system, but it is very difficult and

not always repeatable. The only true, 100% way to release the clutch is to turn the power off and put the bike in reverse. This will release the pressure on the clutch and the springs inside the clutch will return

the rollers back to the neutral position.


To answer #3, there is no way to drive the front wheels at the same time as the rear wheels without the rear wheels slipping. The bike is geared to have a 20% speed difference from the back to the front.

This means that it takes the rear wheel to slip or spin 20% (1/5th of a rear tire revolution) before the front wheel to drive the system. This is necessary to give the bike a tight turning radius and to prevent the bike from automatically "wedging". If the front to rear ratio was 1:1, every time you turn the handle bars even slightly, the front wheels would act like they have a fully locked differential and it would take

you 30 feet to turn a 90 degree turn (like driving a new Kawasaki Prarie with the front gearcase locked). Becuase when you turn, all of the wheels on the bike are now moving at different speeds dictated by the ground speed, and the front clutch would not be able to overrun. With the 20% speed difference, the AWD can be on all the time and it will only be there when you need it. You won't get any of the side effects

of all the other systems that don't allow you to turn the 4wd on and off. Basically, having the front wheels driving the same speed as the rear wheels would be like driving a tank and would be hard on the arms

and not very fun.


I hope I have answered all of your questions and not confused you to much. Browse through the overrunning clutch section on the Hilliard web site (Hilliard Industrial Clutches, Brakes, and Oil Filtration) for more info on how overrunning clutches work if you have any more questions. Have a good day.


Thanks,

Matt Cowen

Engineering Product Manager

Drive Train Products

Hilliard Corporation


phone: (607) 733-7121 ext. 376

fax: (607) 733-1045