Maybe we are missing something here............
You mentioned turning the Hilliard by hand? Maybe you are are testing incorrectly.
From the service manual:
With the Polaris All Wheel Drive System activated (AWD selected), the machine operates as a 2 wheel drive vehicle until the rear wheels lose traction. If the rear wheels lose traction the front wheel rotational speed will decrease, causing the front drive axle speed to exceed front wheel speed. Restricting the rotation of the drive clutch roller cage (2) (see Electric Hub Operation) will cause the rollers (3) to climb the ramps of the cam(5), and become squeezed between the ramps and the ring in the hub. See illustration #1. When the hub clutch assembly, wheel hub, and drive axle are engaged, the front wheels will drive and stay engaged until rear wheel traction is regained.
When traction is regained, the front wheels will overdrive the hub clutch, pushing the clutch rollers (3) toward the lower part of the cam (5), disengaging the clutch. The rollers are held in place by the spring (4). See illustration #2. The tension of this spring is critical to AWD hub operation. Always use the correct spring (refer to appropriate parts manual) and use installation tool PN 2870888.
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 a loss of vehicle control and serious injury or death.
When AWD is selected in a forward gear, current flows through a coil of wire located in the strut housing, creating a magnetic field. An armature plate (1) coupled to the roller cage (2) is attracted to the magnetic field, and resists rotation, creating drag on the drive roller cage assembly. This causes the roller to climb the ramps of the cam, engaging the hub. NOTE: In reverse gear the override button must be pushed to deliver power to the wheel coil. Electric hub engagement offers an advantage over
mechanical systems. When the AWD button is switched off, the machine will have the steering ease of a 2 wheel drive unit; and with the switch turned on, all wheel drive will be engaged whenever the rear wheels lose traction.
Hopefully you are testing with all 4 wheels off the ground and the front wheels mounted - it is possible the front hub is worn out and needs replaced - even if all is the parts were new and known to be working correctly, a worn hub could prevent the Hilliard from locking up.
It's a pain, but you might try swapping the hubs. If the problem moves, replace the hub - if not, continue to troubleshoot the non-working side.
Shop Owner and Mechanic with over 50 years experience