ATVConnection.com ATV Enthusiast Community - What's that reverse over ride down hill trick?

found this:

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. http://www.hilliardcorp.com/mcdboc2.php3
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?
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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 proceding 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 becuase 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 gearcase, 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,