My 2006 Kawasaki brute force 750i non-power steering, is always pulling to one side in 4x4. When i put it in 4, it'll knock then pull really hard, then i'll build some speed (trying to control the pulling as much as i can) and hit the front brake(trying not to flip it), it'll knock then stop pulling. But sometimes it's left, and sometimes it's right. I feel like its very dangerous because i never know when it'll start pulling. Can anyone help me figure out what it could be?