I have about 18 Hr. on my Grizzly and have noticed a slight vibration when the 4x4 button is on and riding, no vibration when in 2 wheel drive. I was wondering if this is due to the angle of the front drive shaft with the u-joints. I had a 2000 Kodiak and when in 4 wheel drive it didn't Vibrate, but it had straight drive to the front and back. The vibration may also be due to the way the tires track. This is a great machine, I can't wait for it to be broke in!