Hey NLATVGuy.. The hillard clutches work the same in forward or reverse. There is no binding in the Polaris 4wd system. The reason a Jeep or the competitors ATVs bind is that they do not have overunning clutches.
Bryce

 

Thanks for the clarification Bryce. I agree that the hilliard clutch works the same in forward and reverse. The difference in gear ratios however (if indeed there is any), would cause the hilliard to overrun in one direction and bind in the other. If the gear ratios are the same, the only way to disengage the front once it is engaged (we know that it engages as a result of the rear wheels turning faster than the front - ie: wheel spin) would be to spin the wheels in reverse. Polaris states that the front engages when rear wheel speed is 20% faster than the front and disengages when wheel speed is the same. In reverse, wouldn't the rear wheels have to turn 20% SLOWER than the front to keep from binding? I think this is why you are able to "wedge" the machine into a true 4 wheel locked state by engaging the AWD in reverse before desending a steep hill - AFAIK this cannot be done in forward. Here is a post from another forum that may explain it better:

BEGIN QUOTE FROM SNOWRIDE OF ATVFRONTIER.COM:

One of the drawbacks to the Hilliard clutch that Polaris uses for 4x4 is that there is no engine braking on the front tires (only the rear) Here's a little trick.


I copied this from another forum. It is an e-mail straight to hillard corporation who supplies Polaris.


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 (www.hilliardcorp.com) 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
END QUOTE FROM SNOWRIDE OF ATVFRONTIER.COM:

 

Hello NLATVGuy. The rear wheels always run 20% faster in forward or reverse because the front to rear gear ratios are always the same. Even though the reverse ratio is higher, the front to rear ratio is the same. The reason you can wedge the fronts so easily in reverse is because when you hit the throttle in reverse, weight is transfered off the rear wheels so they spin easier. Often times you do this on a hill (pointing down) so even less weight is on the rear wheels. It is quite difficult to do the same thing in forward because the weight naturally transfers to the rear axle when you hit the gas.
Bryce

 

OK, Thanks again Bryce[img]i/expressions/face-icon-small-wink.gif[/img]

 

The system is a failure and that’s why keeps changing it!

If you have bought a machine you had better learn to repair that specific year or get a different brand

The Hilliard is a failure ………..true …….end of story.

It was system designed to run conveyors!

 

Hey Zbart1... Every single new automatic transmission on a car today has an overuning clutch in it. So would you say all these cars are failures? Maybe we should use our cars to run conveyors eh!!
Bryce

 

just a question (in Theory) that came up as I was buying a new hilliard cage last week. what if the springs in cage were a different tension? Lighter or heavier.Wouldnt that fix the problem of front end engagging do to centrifigal force - drive shaft spinning so fast it spins gears in front and catches front axles? (like in a snow or ice donut)? Jeff

 

I thought about my post and I must admit a few beers and I was ready to vent!

I don’t want to say that the system is a failure that would be a little harsh to say the least. And I stand corrected.

What I will say is the system when it works is a great system for the average rider as far as the way the system works and the easy steering it offers while still giving you the 4 wheel drive all but the most demanding people need.

The problem is it just plain needs to be more maintained then the “average” rider can do or afford. I really think the system is just a few years from being perfected
(Eliminating the two hub system at least cut down on half the problem) unfortunately the added horse power and increased centrifugal force created a whole new set of problems!

The problem I see is the dynamic forces involved in running down the trail are not really as straight forward as just “ constant” forward rotation but the on off inconsistent surges of power that comes from a piston driven engine. Add to that the fact that it needs almost a “pristine environment” to work properly (that’s why you need to change the fluid so often) that just doesn’t exist in the four wheel world.
I think like over the years they have learned to get an engine to live in a hostile environment you will see them solve the Hilliard problems.

I still think that reality is while much like the guys with the 4 wheel drive trucks and suv’s we think we would like lockers or posi traction the reality is that they are just to hard on the drivetrains and the people who drive them.

 

It seems to me that since the engagement of the overunning clutch is controlled by the drag on the armature plate, I would look for too much drag on the armature plate or addiotional drag on the roll cage. Centrifical force does not make the clutch engage. While the clutch is running at high rates (between the ring gear and output shafts like on ice), the fluid drag on the roll cage could cause unexpected engagement. It could be that a lower viscosity fluid may correct this problem particularly if the problem occurs more often in the winter. The other effect I can think of might be the rate of acceleration, not just speed. In this case, the fluid doesn't accelerate as fast and also causes drag. It could be that higher rate springs may also help, but you might get to the point where the clutches may not engage at all.

It seems to me that torque pulses from the engine are highly unlikely as the culprit because the engine torque pulses are effectively isolated from the drivetrain by the belt. I am not sure I would be concerned about a pristine environment considering, the engine internals require a pristine environment and they seem to run forever.
Bryce

 

I dont know if fluid would"burnout" but a slow leak would be more likely. Not a hard job to replace seals , basic tools etc.Make it clean,dont have a cow about hospital sanitizing. As I said before ,it may be a switch also..deal can tell you what wires to check and how much resistance(ohms?) is correct.