I was playing on the ice yesterday and watching my front visco locking up... it was instant- as soon as I hit the gas both front tires were spinning.

the visco front diff has never let me down-

 

I think Can Am has the best four wheel drive system.

Yamaha, Suzuki, and Arctic Cat are good, but you have to stop and flip a cover out of the way and then push a button to engage the front locker.

Kawasaki is ok, but you need to pull a lever in and hold it in for the front locker to work.

Polaris has an overly complicated system that requires yet another overly complicated "active descent control" system to get four wheel engine braking to work. The Polaris system has a rear differential that is geared slightly taller than the front differential, and a dog tooth design in the front differential that will start to pull as soon as the rear drive slows down (from tire spin). The rear tires have to continue to turn slightly faster than the front tires to keep the front tires turning, otherwise the front end disengages and goes back to freewheel mode. Having said all that, the system actually works fairly well, but not in all situations.

Just last weekend I did a trail in the mountains that had a lot of mud at lower elevations and a lot of snow at higher elevations. The snow was drifted almost headlight deep in places, and the trail was a narrow 50" wide trail on the side of a mountain. If you would have slid off the trail there would have been nothing to stop you until you were at the bottom of the mountain side, 500 feet below. The QE visco lock of the Outlander 1000 I was riding worked flawlessly, and always engaged instantly when there was even the slightest tire spin. It was like having an automatic locker that engages without needing to push a button. And I didn't have to worry about a Polaris like system forcing the rear tires to keep spinning slightly to keep the front tires pulling. This would have been really bad on the side of that mountain, because any rear tire spin relative to front tire spin would have caused the rear of the ATV to track to the downhill side of the trail, and eventually off of the trail. I was real glad I had the ATV I had on that day. No starting and stopping to push a button, no lever to pull, no unequal front and rear tire speeds, just ride and have a good time. It worked flawlessly.

 

can am and polaris get my vote, but there is nothing wrong with the grizzly 4x4 system either

 

I have a Polaris RZR and there 4 wheel setup sucks but is better than the Canam. I like the Suzuki best then Yamaha then Kawi, Polaris , Canam .Honda is really just 3 wheel drive.