I purchased a 1999 Polaris Scrambler 4x4 400 for the drive parts. I have removed all of the parts I will need from it for this project.
Here is a picture of the parts I will be using.
Cvans has the same four wheeler, and was able to copy some information from his manual about the operation and engagement of the front wheels.
"FINAL DRIVE SYSTEM SERVICE Demand 4 Operation - Mechanical Hubs, 1987-1988
In the Polaris Demand 4 Drive System, the machine operates as a two wheel drive vehicle as long as the front wheel rotational speed remains greater than the front drive axle speed. If the rear wheels lose traction the front wheel rotational speed will decrease, causing the front axle speed to become greater than the front wheel speed. The roller cage plungers contact the strut ramps, restricting the rotation of the roller cage and causing front wheel engagement. The rollers will then climb the ramps, becoming squeezed between the ramps and the ring in the hub, and engaging the hub. ,Once the wheel hub, Demand 5 clutch assembly and axle are engaged, the front wheels will drive and will stay engaged until the rear wheel traction is regained. When rear wheel traction is regained, the front wheels will overdrive the front drive shaft, pushing the clutch rollers toward the lower part of the cam and disengaging the Demand 4 clutch.
WARNING: It is important that the front and rear axle drive ratio and tire size are not changed. Changing this ratio will cause erratic engagement, which could result in serious injury or death.
Demand 4 Operation -
Electric Hubs, 1989 to Current
The electric hubs operate in much the same manner M the mechanical system described above. The only i Is that the clutch engages by means of an i magnet and armature plate instead of plung-i aprlngs and ramps. The electro magnet and ar-plate restrict the rotation of the Demand 4 i roller clutch assembly. The advantage of this I over the mechanical is that when the 4 wheel switch Is turned off the machine will have the ease of turning of a 2 wheel drive unit; and with the switch turned on, 4 wheel drive will be engaged."
Upon further research, I have found out that the front wheels are engaged when the machine looses 20% of its speed. For my application, I am thinking that it might be better to change this to about 10% speed loss. This means that less traction will have to be lost for the front wheels to engage. This is something I would like other opinions on.